I've got a Creative Zen (just Zen!) and have been hapily enjoying away for the last couple of years

My partner and I have had 4 Creative MP3 players between us now (though not the Microphoto one!), and I've been impressed with the sound quality on all of them. My Zen Touch was great until a fellow commuter spilled coffee over it

and had lasted me 3 years up until that point.
My Zen has 32gb of memory (can be used for photos and videos as well as music) and has a memory card slot so can be effectively doubled in size (in case your 20gb music collection grows!). This doesn't, however, integrate with the main player, so if you selected 'random play all' then it would only play from the player, not the card. Not sure if this has been changed with the more recent models, but I don't plan on upgrading til this one breaks... It has a decent battery life - I charge it every couple of days but use it for 8-10 hours a day due to an insanely boring job, though obviously if you're watching vids on ther it won't last as long.
Newer models have WiFi and suchlike but as a result, the )just) Zen can be picked up for considerably less than it was when I got it (the Creative site has the 32gb for £120)!