I just got a Rio 600 mp3 player pretty cheap, and I think it's great. It only has 32MB, but I realistically don't need much more, especially not to justify the extra $$ to get a 64mb player. That's just a matter of personal preference, though. About the player itself: It integrates perfectly with iTunes (I didn't have to install a thing from the included CD). It takes about a minute (maybe even a bit less) to transfer a full 32MB to the player. The buttons are laid out well, and I like the circular control thingy. The sound quality is great, and the EQ really works. This thing is tiny and VERY light, which is a great advantage over CD players and such. The screen is easy to read and has a nice and bright backlight. Also, the unit is pretty rugged (it already took a fairly hard bump because I forgot it was in my pocket, and there was absolutely NO damage done at all). Overall, I'm very impressed with this player so far, and would recommend it to anyone who doesn't need a huge amount of storage space.
Note: the 32MB holds 32mins at 128k encoding, 45mins at 96k, and about 70mins at 64k. I actually can't tell much of a difference between encoding rates, and even 64k mp3's sound great, so the storage isn't actually THAT big of a drawback.