I got a creative zen xtra 30 gb. I think its great. Its software works well with my creative audigy 2 sound card. Its battery life beats iPod (new iPod models come close though) and unlike an iPod the battery is easily removable so you can swap it out for a 24hr battery. It is bigger than an iPod, made with anodized aluminum, which is dentable but it has a cool rugged look. Sound quality is great especially with $40 sony headphones and I recommend those not matter what mp3 player you get (Fontopia Headphones MDR-EX51LP). User interface is great too, easy to move songs to playlist, create playlists, delete songs, adjust equalizer, time-scale, all on the go. My volume down button and scroll whell getting a bit slugish but.... Also creative offers Zen micro, 5gb with 12hr bat. Its small, removable bat. Blue backlighting, many colors and both players have signal-to-noise ratio up to 98dB (meaning best audio performance compared to other mp3 players)
I've used an iPod, not impressed with user interface, click wheel is cool but don't like interface. Also too expensive. And baterry life is just too short, can't replace battery and I heard it dies after some time (maybe the older models). It does have cool features like games, calanders, ALOT of accessories (flashlight, laser pointer, microphone atachments). ITs good though, small, cool looking.
Another good brand is Rio. I've used some of their mp3 players and cd players before and like it. The Rio Carbon is 5 gb with 20hr batt. The Rio karma is 20gb with a 15hr bat. It also hasOgg Vorbis and FLAC Support. The Rio Nitrus is 1.5 gb, 16hr bat. and its thin.
iRiver has good mp3 players too. The H340 and the H320 have 40gb and 20gb respectively, both supports MP3, WMA, ASF and OGG music files. Fm tuner, color display. Signal-to-noise ratio Left 90dB/Right 90dB. iRiver also has good flash mp3 playres up to 1gb in storage.
Those are all good brands that you could consider, it mainly depends on what style you like and the user interface. If you are active and run or jog alot, get a flash player, not a harddisk player. Flash players can be dropped and such with out harm..no moving parts....and hd players....try dropping a hardrive and find out.