Not much upside even if Congress does put together a plan with SOME "real teeth" in it.
Most likely, it will be a smoke-and-mirrors job that pushes the problem out just past the 2012 elections. Then we would get a 3% to 5% immediate selloff, followed by some sideways and then a bit of slow recovery as investors realize that the world did not actually come to an end.
Actually, I'm much more concerned with how the 2012 elections turn out. If Obama and the Democrats are not thrown out, then we move past the event horizon into the black hole of economic ruin.