Just throwing in my thoughts on only having watched half the debate...
I think that this went as well for Romney as one could have realistically expected. He was confident and confidence counts for far too much in these. I personally felt that Romneys typical response was "No, that's not what I'm doing, I'm not doing XYZ, that's not my plan", but then never went on to explain what his plan really was, only what it wasn't. I remarked to my wife (who is in the process of shaking her fathers Republican upbringing), that Romneys plan is "Everything that is good in Obamas plan, but without those bad things", sometimes even ommitting to say what the bad things are. "We will repeal Dodd Frank, but don't worry, we will keep the good parts!" That said, I don't know how much his negatives were noticed due to my own bias or if it was apparent for everyone to see.
Obama seemed good enough on his own, but felt more like he was just going through the motions. Obama never made any mistakes, it's just that his performance was flat decent all the way through, no real highs or lows.
Overall I think it was close, but not close enough to call it a tie, putting it in Romneys favor.