I was able to play with this when the founder came to Berkeley. There is some really cool tech behind this, and I was astounded at the accuracy when I tried it out. I'd encourage you to try it out.
I'm really excited for the Grooveshark integration- been waiting almost six months for this. Great job guys! Look forward to an SDK sometime down the road too so we can hook it up to our own apps.
Yes, there is but will be quite hard as with Linux we always have to worry about webcam drivers as they will be very diff. We are looking into this as well.
Yes, we are aware of it. Some AMD and some old Mac processors run behind on some processor libraries we use. We are working to enable them and make it backwards compatible.