I buy my CDs whenever I have the chance. Sometimes I'm forced to download some CDs because a lot of my favorite bands have CDs that are out of print and they have not re-released them and they go for 100+ dollars on eBay (like Mindless Self Indulgence and Dog Fashion Disco;
that's WAAAAY too much money to spend on a CD). I mostly use mp3s to see which albums are good. I don't listen to mainstream music that often (aside from Jpop), so I don't usually run into the whole "only one song is good" problem. And some band's CDs aren't readily available in stores (I'll have to order off a website), so I use mp3s to see if it's worth ordering. I also use mp3s to discover new bands (DC++ has done WONDERS for me). If I'm REALLY addicted to an artist at a certain point, I'll download a lot of their CDs because I don't have the money to buy them all (like I just did with Faith No More and Cannibal Corpse). I haven't had a job for almost a year, so my CD purchases have been really small (I think the only CDs I got were pretty much presents), but now that I have a new job I'll be buying more CDs. If there's an artist I absolutely love I'll buy their new album on the first day (come April, it's gonna be Dog Fashion Disco!).