I Love the new split screen thing in Windows 7
But a nice feature that could be helpfull when two applications run split screen would be to connect the resizing, such that when i increase the width of VS, the width of Adobe Reader decreases and vice versa.
If the windows shouldn't always be connected, a visible handle with the correct affordance between the windows would allow for both connected and normal behavior.
This could even be extended such that whener two window frames touches each other, that handle appers allowing connected resizing.
Here I will write, what I need to be sure that I can find again, and far more which I probarbly don't need to find again :)