Pros: The sound, the sound, the sound (also the price)
Cons: nearly everything else
This is pretty much the same weightless, rickety, tiny player apparently offered by Kogan, oRiver, Ritmix, etc. It comes decently boxed with a soft pouch, USB cable, and nice looking (if unremarkable) IEMs with spare shirt clips. I was fortunate to get mine for $50 shipped to the US from Singapore through a Head-Fi ad. (Admittedly, this price gave one some pause considering Kogan's original $30 AUS price point - and something like the xduoo x3 now available for under $100. But I'm glad now to have done it.)
The unit is a light, semi-fragile fingerprint magnet. I improvised a thick, clear plastic cover for it out of a dollar store micro-cloth case.
If anything, the features are overly ambitious - offering a low-res camera to take horrible stills & video, along with an added FM radio, eBooks - even Atari-esque games, all in one, tiny package (reminds me of my Best Buy Sansa Insignia 10 years ago). No wifi, BT or streaming features at this price. None of these add-ons will be the least bit interesting to a modern budget smartphone user. The low rez screen soon had a single scan line of white pixels (which didn't affect readability). Inserting a (only up to 32gb) micro SD card into the little slot takes an uncomfortable amount of force. The frustrating UI and stiff buttons are more Dollar Store calculator than iOS iPod, for sure.
But, enough about what it looks like, it's all about the SOUND, isn't it? And, indeed, it does live up to the "Kogan hype" of bright, detailed SQ. I've been staying up 'til the wee hours, replaying, in wonderment, the same instrumental sections over and over. All this with ordinary WAV and 320 MP3 files. The M90 also plays FLAC, but not at 24 bit.
Even when combined with an open, airy earbud like the Monk, it has a surprising amount of subdued bass, serviceable enough for occasional garage, hiphop and EDM, even if it wouldn't be your first choice. My $3.99 Monoprice Reflective IEMs will instead squeeze out a lot more sub-bass - and at a much lower volume setting - while comparatively dulling the rest of the dynamic spectrum.
There are no custom EQ settings, which I normally avoid. But the "Pop" EQ preset pushes balanced bass and some mids up without over-cooking the highs to a forced or artificial sound. This lets select recordings reveal details more clearly - and at a considerably lower volume setting - with the Monks.
Using this preset, I began noticing INCREDIBLE subtleties with dual acoustic guitar strumming, rim strikes, xylos, vocals, and maracas (ooohhh....those faint, ghostly maracas!) in Costello/Bacharach's "Painted from Memory" (yeah, I'm an _old_ dude!) :)
Beck's folksy, audio-benchmark albums, OTOH, probably sound better with just the flat setting - but you may still need more volume to really catch the sneaky stuff going on in some tracks with the Monks.
It'd be hard to find a more cheap (and weightless) combo than a Kogan clone like the M90 with a Monk+ plugged in - $50 for all before postage is added (or $35 w/ original Kogan!).
It simply must be the Biggest-Bang Sound for your Budget-Audio Buck.
They may not last too long, but it'll be a fun ride!