Dunno, looks like Gallup had Obama 48 - 42 over McCain prior to the DNC, and 50 - 42 now. That's a 2 point bump from pre-convention polls.
Rasmussen has him going from even at 47 (with leaners) the day of Obama's speech to 51-45 now, for a six point bump.
Frankly, that's not very good when the RNC is still going, after having been interrupted by ma nature. Post convention spikes are usually larger for a lead candidate.
Things are tighter than they should be at this particular time, whether democrats are willing to admit it or not.