Some netlabels seem about as reliable (in terms of quality) as a random cm/8bc download, but I keep coming back to the more reputable ones to download fresh, good music. Bandcamp is convenient, and one of the few ways I still randomly listen to albums I've never heard of before. It's still hit/miss when it comes to quality, but as DKSTR pointed out, at least the player is good enough to account for it.
EDIT: And yes, net labels have helped me. I do virtually nothing to promote my own music outside asking labels when I get some songs bunched up, and according to last.fm i still have a bunch of listeners. Now, the proud part of me likes to think it's because my music is good, but it's probably mostly because I've gotten in contact with good labels that already have a lot of quality content relevant to what I want to release.