I had a bit of a play and experiment with it earlier today, and whilst
I am pleased that Adobe understand the need for cross-browser testing,
I feel the execution of their solution somewhat lacking.
I found the experience of Browserlab to be painfully slow, however I
am willing to see through that for the fact of it being in beta and no
doubt hammered due to it being announced today. The main issue I had
was that the captures that it took weren't interactive which meant
entering a URL manually each time you wanted to check a webpage. This
could become tiresome and laboreous for a large website.
At the moment I think I'll stick with Virtual PC and multiple installs
of Windows/Linux with different configurations.