The first debate I felt it was pretty even, with Clinton scoring some strong points and Obama doing so as well.
I think Obama is ahead in this one so far. Every difference that Clinton has tried to isolate Obama has responded to in a convincing way (at least to me, of course). I think Clinton did well overall in health care - I would expect her to be ready to go on that subject, but Obama held his ground better than in the first debate. But in the other topics so far, I think he's come out ahead. His response to "I'm ready to lead from day 1" and especially his response to Iraq really hit the point home really well, I think.