I don't understand the part about browser tabs - when I want to drag something from one tab to another, I just hover the mouse over the destination tab and the browser switches to that tab. Takes about a second.
How do you do that when the other tab is buried under three other browser windows in another space? Possible, but this makes things a lot easier. Then again, maybe the way I leave tons of stuff open across lots of spaces is just the sort of workflow that something like this is meant for...
I guess I must not have that many browser windows scattered around the place when I'm using OS X or Windows and on linux I use a tiling window manager, so its trivial to tile both windows side-by-side and then drag between them.
