Pros: Android, quite light, HDMI out, kickstand
Cons: Battery life could be a bit better, no line-in, "floating design" takes getting used to
Cowon've ventured into android before, and with the D3 plenue, it was thought that they'd hang up and stick to their own OS, but they've brought out the Z2, and it does android right!
The first thing is the fact that, because of Android, the Z2 not only has a much easier to use (and learn) interface, it means that you have the opportunity to switch around nearly everything. From the music player, to the home screen, and everything inbetween. The only down side is that, because Cowon aren't Google Certified, you don't have the Play store, but that it something that can be remedied if you were to root the device. By doing so, you do unlock the potential of the phone a bit more.
It also feels a lot nippier than even the J3, from the responsiveness of the touchscreen, to how fast it actually does things on the screen. Unlike the D3, the Z2 is actually kinda fast. Sure, it's not exactly a powerhouse like android smartphones out there with their dual and quad-core processors, but it'll still handle most of what you can throw at it. The only thing about it running Android is that you sometimes get a slow moment here and there, but it's nothing that being patient for an extra 3 seconds won't fix.
The great thing about the Z2 is it's connectivity. It has Bluetooth and Wifi, meaning you can use it as an iPod-touch-a-like with apps, the internet and such, with the obvious penalty to battery. Bluetooth handles not only audio, but file transfers as well, so you might be able to get all your music on by bluetooth if you're short on time and have your phone with you as well. It also has a micro-HDMI out, meaning if you wanted to listen to your music on the big screen, you could do it in a little bit of a sharper way, instead of having to use what's becoming a slightly dated composite output. It doesn't have a line-in, however, so if you wanted to record from a line level signal you'd probably need to wait to see if something in the future does it.
The design of the player is a little bit of a "love it or hate it" thing. It's got a simplistic design to it, quite rectangular with a part that comes out at the back to give it that "floating design." I don't really mind whether it looks like it floats or not, but it does make it a little bit easier for me to hold. A lot of people do say that it makes it a little bit harder to hold, but it's probably one of those things you'd get used to. The door for the Micro HDMI, SD and USB actually becomes a kickstand for the device, so you can keep it propped up for when you're watching a video. Something quite useful.
The only way to describe the SQ is that it's classic to the Cowon line of players, in that you have the same, if not slightly more freedom in the effects you can get in JetEffect 5, and that pretty much makes it a good pick for a new PMP.
The biggest gripe I have is the battery life, in that it pretty much lasts a day or so of use (pretty much comes close to it's 22 hour battery tag when you have it at brightness level 1) compared to the J3's 60+ hours of music use, and even the iPod touch's quoted 36 hours. I do think, however, that if you're using it as your portable player while you're in the city, on the way to and from work, you'd barely notice a change, except that you'd most probably need to charge it every night or two instead of every 4 days or something.
In general, if you're looking at Cowon players, and you're looking for something new, the Z2 is pretty much the choice to make, it's quite a light player, that can give you a great sound for whatever it is that you need to drive. Is it a complete J3 replacement? No, but it does come close enough