I downloaded symphony os last weekend, but I will not have a chance to install it until tomorrow. I'll post my findings when I have an opportunity. However keep this one thing in mind, Symphony OS is still in Alpha testing therefore it may still be quite buggy.
I must say that it does look really good I love the layout of the desktop.
Btw have you seen the demo for Sun's project Looking Glass
OMG it is one of the best looking desktop's I have ever seen. Absolutely jaw dropping.