emusic gives you a non-protected mp3 at (arguably) a higher quality bitrate. They work fine in iTunes and with an iPod (i use it on a Mac). Their pricing is much different - you pay a fixed amount per month which gives you a certain number of downloads per month - great for sampling new music (and you own the songs, you are not renting them).
The only consideration is if you would download enough to make it worthwhile - I find they have a pretty good selection of alternative music, but not mainstream artists. Highly recommend checking it out.
I find emusic and iTunes to be complementary.