Pros: Cheap price. MicroSDHC slot. Supports flac. Can run Rockbox firmware.
Cons: Cheap build. Makes some unwelcome noises. Original firmware can't do gapless.
I used the player with the original firmware and I also installed Rockbox. I'll deal with notable points of each firmware.
It's cheap. This needn't be such a bad thing as in a bigger player. Cheap stuff can work fine. There is no mystery involved in assembling/making a small plastic case or a two colour display or some buttons. The Clip's clip still clips after 28 months and the buttons still work. The one component that was always much too cheap and has become worse is the headphone socket. It doesn't hold the headphone jack tight and it has become a little looser over time. In contrast the headphone sockets in my other players and phones and tablets all have a small spring clamp in the socket and any jack inserted is held securely. With the Clip+ noise from the poor connection is audible every time the player is moved, such as while in my pocket as I walk. To me this counts as a major failing. I bought the Clip+ for use while I'm out or busy but this is where its most prominent shortcoming is evident.
The microSDHC slot is a great feature. MicroSDHC cards have tumbled in price and it cost me less than £25 to add a good quality 32GB Class 10 card that works perfectly. The internal 8GB of storage is very slow.
The radio is basic but decent enough. If you live somewhere with strong FM signals and little interference you'll enjoy it. It's not a great radio with weak signals.
The player is so tiny and light that you can clip it onto a belt or sleeve or pocket and just forget about it.
My review doesn't cover Slot Radio or Audible audio book support as I don't use either facility.
I'm not sure there's any more to say about the hardware.
Notable features of the OF (Original Firmware):
Gapless playback is not supported even for those formats which natively support gapless (flac and ogg vorbis). Some people don't seem to mind clicks or gaps artificially inserted into performances. I definitely do. Bad Sansa.
The OF is database only. It can present a "browse by folder" option but this actually depends on the database so it will only show you files it knows. Refreshing the database can be very slow indeed if you have a large capacity card in the slot. This is most definitely a deficiency as it's inefficient and inconvenient enough to become annoying.
Aside from that I think the OF interface is pretty reasonable. It's easy enough to browse by folder/genre/artist and so on.
Notable positive differences of Rockbox over the OF:
Gapless playback. It works! It works in every format which can support it.
You can choose not to use a database. Even if you use a database it refreshes on changes extremely quickly, just a few seconds.
You can choose to browse by folder, and which types of files you want to see.
Rockbox supports many more audio codecs. It can play your m4a files or midi tracks or the weird format from your old skool game.
There are numerous other features and enhancements (bookmarking, sleep timer, wake up alarm, games, apps etc.) but in this review I want to concentrate on the player and its core task - music playback.
Firstly the sound quality is basically fine. It's neutral. There is no silly bass emphasis or nerve jangling highs. It works well with my typical low impedance IEMs and 'phones (various Sennheiser, Shure and Sony models from 16 ohms to 32) and also seems to put out a fair bit of power for a portable device so can drive plenty of full size headphones if they are sensitive enough. It easily drove my Sony MDRZX700 headphones (106 dB/mW and 24 ohm) but wasn't really capable of driving an old pair of Sennheiser HD 500 (101dB/mW and 150 ohm).
Some people note a difference between Rockbox and OF and claim one sounds better than the other (or one is right and the other is wrong). This can get very exciting with accusations of deafness, bias, stupidity and all the rest. There can be differences in the sound because each firmware does some things differently:
Supports 44100 and 48000 Hz files without sample rate conversion.
Has a pitch error so 44100 files play back at the wrong speed (you can hear this but you might not notice it). 48000 Hz files have correct pitch.
Dithering seems to applied and cannot be switched off*.
Replay Gain is off by default.
Only supports 44100 Hz files internally. Uses a linear sample rate converter for other rates.
Plays back with no pitch error (or error so small you need measuring instruments to detect it).
Dithering is not enabled by default (user can enable it).
Replay Gain by default is in mode "Track Gain if Shuffling". This means it "Maintains a constant volume between tracks if Shuffle is set to Yes. Reverts to album mode if Shuffle is set to No" (from the Rockbox manual). Clipping prevention is off and pre-amp is set to 0.
So if you play a 44100 track in each firmware at seemingly identical volume (max in OF and 0 dB in Rockbox measure the same on my Clip+ into a recorder) it's possible to notice differences in level (due to Replay Gain in Rockbox) and pitch (due to error in OF) and perhaps a difference due to dithering.
If you play back a 48000 Hz file the OF's pitch error is gone. There is still the possibility of Rockbox's Replay Gain altering the level. There is a definite change in the sound in Rockbox due to the resampler. This is completely unmissable with 10000 Hz sine wave or if you want to hear it in real music try a track with some cymbal splashes and hi-hats. It's horrible.
So people claiming to hear a difference between the firmwares can be reporting a real difference. And people reporting no difference may also be right.
Almost all of my music collection is 16-bit 44100 Hz audio from CD so Rockbox's sample rate converter hardly matters. Replay Gain can be toggled off or its settings changed. Dithering can be enabled/disabled as preferred. But in the original firmware there's nothing you can do about the pitch error (and you can't switch off the dithering). Rockbox clearly has an advantage over the OF for 16-bit 44100 Hz audio. It can play it back at the correct pitch without introducing artificial gaps. If you are that rare person with a huge collection of audio at 48000 Hz (maybe a big collection of music from DVDs) then the OF is better. If your priority is playback of 88200/96000/192000 or even very low bitrate HE-AAC then this isn't the player for you.
Output level is pretty good. Assuming no positive increase of level from Replay Gain you won't get distortion even at maximum volume in the OF or up to 0 dB in Rockbox. Rockbox can artficially go louder but you might not like it much. There are louder players but the Clip+ should satisfy anyone who hasn't already damaged their hearing.
The Clip has an unexpected feature - a collection of squeaks, clicks, screeches, buzzes and rumbles that if emitted by an adult human might qualify them for psychiatric evaluation and some interesting pills. Some of these noises arise from button presses or play pausing/resuming/stopping and are tolerable. Others can appear in playback. I assume the player's CPU and/or memory get maxed out (maybe I'm wrong) but you can sometimes get the kind of annoying noises you'll know from cheap PC boards with integrated audio. On one occasion my player made a nasty screeching sound for a second or two instead of music and did so in the same place several times. I powered it down and up again and all was back to normal. On another occasion it did a similar thing but distorted as though clipping - again it was repeatable in the same place in the track and powering down solved the problem. Sometimes a piece gets to a quiet passage and I notice there shuffling/rumbling noises that don't come from the music file. Again powering down and up fixes it. I'm glad the player can resume from the same point. Occasionally it fails to complete playing a track and just jumps right to the next one. So Tourettes wasn't all, it also has Alzheimers. Making whacky noises and forgetting to play a track right through isn't exactly audiophile territory and does reveal the Clip+'s lowly origin. But for the most part it does play back perfectly normally. Until it doesn't.
How to minimise the noises and dementia (assumes running Rockbox):
You need to minimise CPU and memory load so:
Don't enable the database (or enable it but disable auto updating and gathering of runtime data)
Don't enable dithering
Don't use EQ, crossfeed, tone controls or anything that touches the audio.
Luckily normal playback without modifying the audio sounds very good.
When it isn't making unwanted noises it's hard to fault. When it is making unwanted noises it's hard to listen to. The headphone socket is the weakest part of the player as it's not replaceable, is of the lowest possible quality and if/when gets noisy you can't fix it. Assuming your headphone socket is OK then Rockbox turns a player with huge convenience but hardware and firmware problems into something extremely appealing and enjoyable to listen to. Until the headphone socket breaks.
If I could rate the player and the firmwares separately I'd give the player and OF 2 stars with 4 for value. Rockbox would get a straight 5 stars, lit up and heralded with a fanfare. Rockbox rescues the player from being a joke (wrong pitch!), makes it really appealing in many ways and gets the best out of the player but there is no getting around the deficiencies or limitations of the hardware.
It is very, very cheap. It can be terrible, it can be brilliant. But it's always cheap. So am I, and that's why I bought it. If you're cheap you'll probably like it too.
*I noticed a perfectly silent 44100 Hz file played back silently in Rockbox but with a little noise in the OF. There was no EQ applied or sample rate conversion. If I enable dithering in Rockbox I then get the same quiet background noise as the OF produced.