Reading over his Wikipedia entry, I think Graham would be a pretty good pick for Obama - experience (both as Governor and Senator for 28 years), National Security credentials (cosponsoring the bill to create a Director of National Intelligence), wins in Florida with about two thirds of the vote... It sounds to me like he'd be a pretty good pick for VP, backing up Obama on his potentially troublesome areas, although I don't know how well he and Obama get on at a personal level. If he can deliver Obama Florida, and if his relatively right-wing positions help in SC, it could be a very interesting result.
Yes I think he would be a good pick for Obama on all those counts. The only thing is that he is as old as McCain...72 in 2008, 73 in 2009.