I think I got through the first page and a half. I'll stop there and give my two cents.
My old MP3 player was a Rio. A FOUR YEAR OLD 128MB RIO.
I finally gave up on it (the battery life had reduced to about 30 minutes) and bought a 1GB Shuffle in February with my tax refund.
Belt clips suck. I had one for my Rio and if I ever tried to clip it on stuff, it might either fall off or it would somehow get caught on the headphone cord or something. I usually gave up and threw the sucker into my purse or pocket.
This battery life problem people claimed with the Shuffle? Yeah, that tends to happen when you don't cycle it. I almost always discharge mine completely before recharging it, and I'm charging it, at most, a couple times a month with normal use (to and from work, approx. an hour a day, sometimes more).
The only reason I'm looking at replacing my Shuffle with a Nano now is because I'm starting to get close to that gig limit, but there's no way in heck I can use 20gigs. That would feel like the biggest waste to me, to have a clunky 20GB in my pocket with maybe 2GB of stuff on it. As for $250, I've known about their student discount for awhile and that will at least knock it down to $230.
I looked at the Zens people have been referring to - that the heck is the point of having rounded edges/corners on the back with sharp edges and 90 degree angles on the font?! So it can either bulge out of your pocket akwardly or dig into your thigh? And in all honesty, the button setup is just akward compared to the lovely little circular thing I have now. Even my Rio had a circular control setup.
And um...earbuds suck because it's physically impossible for me to wear them.