A few months ago, I resubbed to emusic.com. I'd subscribed a few years ago, and lost interest in a couple of months, but this time I'm rather liking it.
In no particular order, what I like includes:
No DRM. I don't have to burn a disc and rip it to take the tracks to work with me, like I do with iTunes. Or to put it differently, I don't get the whole you're-a-criminal-and-no-it's-not-your-music vibe that iTunes gives.
At roughly 25 cents per track (or less, if you get their bigger subscription), I don't feel like I have as much risk getting an album without hearing it first. So far, I've got 16 whole albums and parts of a 17th, and I've made repeat listens to 5 or 6 of them, which is better than one per month. So I'm paying less than $10 per good album, and getting 3 extras to cherry pick from.
It's quite easy to find stuff to try out. I've got a queue of about 30 albums that I'm considering getting, a list of "neighbors" with similar tastes, whose lists I have yet to explore, and a growing list of articles and reviews from the eMusic folks to check out when those lists shrink down a bit.
The biggest downside, of course, is the 30-second previews. Had I heard the whole album beforehand, there are a couple that I wouldn't have wasted time on, but that's life. But again, I don't mind the duds, as I'm still spending less on average for good music.
Another slight downside is that there are no major labels. I say slight, because my focus isn't so much on getting all the songs I used to listen to on the radio, but on finding new music that I like. But I would have preferred, for example, to have gotten my Jack Johnson Curious George CD from eMusic rather than iTunes. So it's a slight problem, but I blame the major labels for being <insert obligatory RIAA insult here>.
Anyway, the bottom line is that eMusic.com is a good thing, and worth the $10/month I'm sending them.