48 - 42 (+6 Obama) on the Gallup Poll; Rasmussen's currently tied at 47/47, but the explanatory text suggests that tomorrow's numbers are going to be more Obama-friendly (they float the concept of a possible 'modest lead,' which means... I have no idea). While this technically represents Monday through Wednesday, today's numbers probably are not taking into account the Wednesday lineup of speakers, which means that the full impact of Bill Clinton's speech will not be reflected in the polls until tomorrow, and the full impact of Barack Obama's until probably Saturday. The first is further better news for the Democrats; the second will be good or bad, in direct relation to Obama's speech.
All in all, based on today's Gallup number, I think that seeing a +10 bounce for Obama by Saturday in either it or Rasmussen is a good minimum criterion for being able to say that Obama had a successful convention. McCain's people were suggesting +15/+16, of course, but that was just them having fun.