I just bought one during the last woot, and dang if I'm not impressed with it! I had some 4gb microSD cards lying around, so I expanded it to 8 (and set up 2 cards with it so I can swap it like media). I think that next month I'll grab a 16gb card to take it to 20gb, which should still have the cost under 50 bucks for 20gb flash memory player. I've read that it's compatible with up to 32, but those are still pretty costly. Though you're not going to find a small player with 36gb of storage for as little as it would cost you to put those two things together.
What I like: It's little, it's cheap, the screen is surprisingly bright, colorful, and easy to see. I stab expansion... stab stab stab. I also appreciate that you can access it like a hard drive and just drag and drop files onto it without needing a cumbersome interface program that is either proprietary, poorly made, or a resource hog. I haven't run the battery down yet, because I'm still constantly plugging it in to screw around with it, but it seems good. I watched a little more than an hour of video at a stretch and the battery was holding up well. The interface is mostly intuitive, though the click positions on the wheel don't necessarily make a lot of sense. Left and right will skip forward or allow you to scan, up is play/pause, and down is menu. My fingers want up and down to be volume, but you turn the wheel for that (it's an actual wheel). So sometimes which motion will translate to which action in the menu aren't intuitive for me, it's not like it takes more than a few minutes of fiddling with it to get he system down.
What I don't like: It's a bit slow booting up. The video converter program is slow and has issues with certain video formats m4v(? Is that right? Whatever MSNBC offers their broadcasts in), VOB, and some others it just will not work with. HOWEVER, there is a free program called "Video4Fuze" that has crunched everything I've thrown at it! I have converted DVDs, video podcasts, other DivX files, and just about everything. It also seems to work a bit more quickly and reliably than the Sandisk converter. Also, you don't need your device connected to use it! you can dump videos in a folder and put them on at your leisure.
I wish I had a reason to buy a second one, because i would... but I already have too many MP3 players and people think I'm crazy.