I use reverbnation. I am also on soundcloud though.
I prefer the community on reverbnation. It is a lot easier to find new, unsigned music on there, and people tend to commicate with each other which is cool. And the ranking system provides a mild yet addictive "gameification" to the online promoting thing (for better or for worse!)
RE sound quality
I posted this recently on my studio's facebook page. It may be useful for people on here too!:
"Useful knowledge here for all you musicians with music on streaming sites: It transpires that a lot of these streaming services work at 128kbps. I have just replaced a bunch of my work on Reverbnation at this rate. My MP3s were at the higher rate of 192, which one would think would sound better! Alas, this created dithering and distortion when streamed due to the algorithms used to convert to the songs to the correct bitrate. At the lower rate everything is MUCH better sounding. Always check the uploaded files on the service itself, and bear in mind this little piece of info. I now keep work as full sized wavs, high bitrate MP3 and 128kbs for online services. Class dismissed!"Also,converting to MP3 should, I say SHOULD, have only a very small detrimental effect on sound quality. If you use the right encoders and bit rate, you should sound like near CD quality. If the quality drops significantly, re-evaluate HOW you are converting and also my advice above. If it sounds good offline, but the stream is naff, it is not the MP3, it is the site's algorithms...
Also, unmastered or badly mastered songs will suffer more from conversion to MP3. Nowt much you can do there....
There are other variables, but that will do for today
Hope I have helped