He didn't attack Romney on the 47% comment nor the lack of tax returns. He didn't make eye contact with his opponent and generally appeared disinterested and at times annoyed.
As it stands, if Obama had mentioned it, it would have appeared petty and self-serving (remember he can't appear to take unreliable information at face value) and he gains way more by not mentioning it. That way, the lack of mention will be noted in the media, followed by another recitation of the video.
I suspect no-one has spoken to him like that in 4 years.
Actually he has had several run-ins with press and civilians along much terser lines than what he saw in the debates.
Edit: I believe that Obama's apparent aggravation and attitude was a direct result of his party attempting to cast him as a stronger president in response to the accusations, and apparent truths, that he was weak on policy. Preferring, as he did, to negotiate rather than force a ruling.
Romney was prepared, made a good presentation, while his plan details are still sketchy he came out on top on overall performance and prepardness. In the past Romney suffered by letting his opponent define him and he would only react. This time he set the tone and held himself well.
I disagree, I felt he allowed the president to attack him while he fended off the attacks by breaking "the covenant" of the political race. You see, both sides fudge the numbers a little in their favor. The "5 trillion in tax cuts" that Obama seemed intent of skewering Romney with is a fudge of the numbers for Romney's 20% tax cut*, which would cost the government almost 4.9 trillion in revenue. Obama tried to spin this by fudging the numbers of the cost and using that instead of the percentage, because a 5 trillion dollar loss in revenue for the government that is already trillions in debt sounds ridiculous, while a 20% tax cut sounds wanted even if they're nearly the same thing. Because Romney knew they were going to play a numbers game (Democrats played their hand already last month), he could sit back while Obama said "5 trillion dollar tax cut" and reliably, though somewhat churlishly, say that "There's no plans for 5 trillion dollars in tax cuts in my economic plan". He could, and probably would have, said the same thing if Obama had stated it was a 4.9 trillion dollar tax cut.
Either way it's an argument on how the situation is stated, and it's one that the Republican party is well versed at.
Remember when we started calling it "Obamacare"? The people to coin the phrase were the republican senators and congressmen in opposition to it. The name stuck. Now, despite the fact that the plan was actually based off of the one created and enforced by Romney in his state, the republicans can completely separate themselves from the entire thing.
Remember "Death Panels"? Another slogan tossed out by the republican party to describe what was named the "public option".
They've become exceptionally good at spin.
*something that would be devastating in it's own right to the country anyways
Look, I want to point something out about taxes. It's not the federal taxes that destroy companies and have them searching for outsourcing, it's state taxes. The Tea Party movement started in New York City as a libertarian movement, and as well it should have. If you travel around the city or any part of upper New York you'll find hundreds, even thousands of small and large businesses that were forced into foreclosure or relocation because of state business taxes within New York. This spawned the first "New Tea Party" demonstrations. These were picked up on by republican talking heads at radio stations around the nation and soon new "Tea Party" demonstrations popped up no matter what the state or local tax rates were. These new movements began to decry overtaxation by the federal government even though the tax rates were, and still are, the lowest in 50 years (which is financially bleeding the country dry). This is where the focus on taxes came in. It's a huge power grab by one party that's based on misinformation and even no-information.