One option that has not been mentioned, and which doesn't meet all your specs -- but might be worth considering.
A Palm. My Tungsten E (just discontinued in favor of the E2, but still available new via 2nd party vendors) works surprisingly well as an mp3 player -- and still does all the things I actually bought it for.
Battery life is not even close to 15 hours -- I think about 1/2 to 2/3 of that? -- but it recharges easily with the included power cord. You need
cards (they fit in the expansion slot) and Palm RealPlayer (a card and RP came free with mine, but that was a special bonus). But that essentially means unlimited storage space, with enough of those little cards.
Playlists are easy. The Palm has a (not very high power) speaker, as well as a phone jack.
The Tungsten E cost me $200 (-10% discount), and the new E2 is $250. Cards vary in price and size.
And my Palm holds lots and lots of fic . . .
