I looked at a lot of small flash players, and their designs all had some issues. I ended up buying a Fuze because it seemed to have the best hardware design, it took expansion cards, it worked without special software (sorry ipod and zune), and it had a screen I could read without squinting. The software is as good as any other manufacturers.
But, for the last several years I’ve been using an old iriver 120 with rockbox, and it spoiled me. The user interface isn’t great but the listening experience is superb.
Features like Replaygain support, conditional crossfades depending on operation mode, gapless playback, unlimited playlists, browse by folder, and all on an ancient (in the mp3 world) player.
Do any mp3 players do this out of the box? I don’t know but I doubt it. When you have a team of dedicated hackers writing open source systems you can get some great stuff, if you have enough patience.
From where I sit the Sansa support on this forum has been pretty good, and their updates have solved some problems. Kudos. On the other hand, if an mp3 manufacturer were to actually work with the rockbox crew to add their feature set, I think they could build one killer player.