All of my music that I have digitally ripped from CD, I do in the FLAC format (compressed lossless). I figure, why not have the same quality as the cd? Space isn't an issue with me.
A CD that has been ripped as FLAC is about 350-500MB, so a 16GB portable audio player would be about equivalent to a decent sized CD wallet. I've been eyeballing the
Cowon iAudio7 for a while now, as a replacement for carting CDs around. 16GB (flash) is about $140