Ive used Blip on and off... sometimes it's a lot of hard work to find the good stuff. But maybe that's how it's supposed to be.. a little reseach can repay big time.
But on the other hand.. Last.FM is much more accessible, and runs more smoothly, with a whole world of info and groups etc. Last.fm is great for music discovery, and hearing stuff you never knew existed; with quite a lot of information about the band/artist etc.
Whilst Grooveshark.com is pretty good; although a little less classy. Grooveshark will find music for you, if you know what you are looking for. Not so imformative, and slightly anonymous feel to it all.