I must say..
Its pretty decent concerning Music Mixers. I even like the idea of a music portal. But I see 2 things that could be improved on.
1.) The Lag. Yes I know you got PMs and E-mails and shit about it being laggy but, hey noone likes lag. And I don't understand how its lagging either, considering I got a 1gig ram system built with a 3.0ghz processor...hell it makes no sense.
2.) The instruments took a trance, techno, and percussion step into the music industry. I believe the one thing you lack, I mean REALLY lack, is some guitars ya know? Make it more diverse concerning instruments lol.
Overall - 7/10 because of the somewhat annoying lag and lack of selection of different genres, but because of the omfg outstanding idea of a Music Portal and its really simple to just make some music.