I didn't really get an opportunity to get involved there.. it started a bit before midnight, then I had to go to bed. I did doodle this:

while I was testing the whole screen sharing thing, though.
Notes:
* Browser window and window to be shared must be on same desktop/virtual desktop. Probably on same monitor too (I only have one so I can't test that.)
* Minimizing the window you are sharing causes the screen-sharing to lose track of the fact that it is sharing that window (so when you restore it, it doesn't continue sharing)