I have a Cowon S9. I love it! As most people said, the AMOLED screen is amazing. The audio is wonderful, and I love the Jet Effect 3.0 and BBE+. The sound (to me) is much more detailed, because the settings are pretty specific. There are a couple of sites (
anythingbutipod.com and
iaudiophile.net) that can help you with the EQ if you don't feel like toying with it. Battery life is great.
A lot of reviews have said that the UI is troublesome, but I learned it pretty quickly. It did not take too long. I like that there are hard buttons on the top of the player.
Though I'm not using it, I really like Claw's UI, because it makes the player more customizable. The only drawback to Claw's is that you may have to deal with a 1-2 second delay, but to me that isn't too much of a big deal.
Some don't like that it feels lightweight,because it doesn't feel sturdy. Despite being made of plastic instead of metal, I think it's pretty durable. The screen is made of tempered glass so it makes it much more resistant to scratches (It's not scratch-proof). No Wi-fi? I wasn't looking for that in a player anyway.
I've also read that Mac users may have some trouble, but there's a way to fix that. I don't have a MAC so it's not a problem for me.
The Firmware updates are pretty good from what I read. If they take care of it like they did with the D2 (which I hope), then I think this mp3 player can go pretty far.

Isn't it pretty? (I hope the picture is not too big.) And those bubbles on the screen are from the plastic film that's still over it. I don't want to take it off just yet. Hehe.
BTW, this is my first mp3 player. I've been using CDs and a CD player for the longest time. I'm gonna miss that thing... Ok, perhaps, not that much, but I'll miss making people smile when I pull it out.
I have tried out other mp3 players as well, but I really do like this one. The s9 may not suit everyone's taste, but it suits mine.

Sorry that it's so long...