Not anything new, but today it helped (ok, at least seemed to help, I'm lacking my empirical data matrix) un-hang a beachballed Safari.
All you have to do is launch Activity Monitor (which just runs the "top" command, like in the Terminal) and it seems to unhang, unfreeze, unbeachball a stuck app.
Does it really work? I dunno. It seems to. It just did. Or at least seemed to. But is it falsifiable?