Here's the take from two of the most savvy observers of US politics. First, Gerry Baker says Obama had a tough night but handled it well, and got the kind of much needed grilling he needs in preparation for the general:

If you want to know who lost most from this debate you need only look at the ranting reaction of Obama supporters everywhere. Daily Kos, Huffington Post, Andrew Sullivan, all absolutely furious with the debate's moderators for asking supposedly cheap questions, largely directed at Obama. [snip]

Pace the denunciations of the Obamaniacs, I think this sort of testing is exactly what Obama needs. The Obama supporters are furious that there weren't more questions on policy. But we know why there weren't. The two candidates don't fundamentally disagree on any of the big issues. And ask yourself this. Has Obama become the Democratic frontrunner because he has persuaded Democrats his policies would be better than Hillary's? No, I don't think so. He has persuaded them that he is the more electable and the better equipped to put the Democratic case in November. As he becomes the presumptive nominee it seems reasonable to me that he should be ruthlessly examined on all these questions. Tonight he was, and as it happens, though he looked defensive at times, he handled most of the pressure well. He will get a lot more of this from the Republicans in the next six months.

Toby Harnden of the Telegraph thinks Obama didn't handle his bad night very well, but that Clinton probably won't benefit from it:

It was a pretty horrible debate for Barack Obama, by my reckoning, probably his worst. He was treated like the clear front runner he is with a barrage of tough questions but seemed almost affronted by this and did not respond well.

Hillary Clinton lambasted him repeatedly, stating that the Republican attack machine would get him in November and then proceeding to attack him in exactly that fashion. And there's the problem for Clinton. Even when she lands punches, she comes across as strident, negative and in league with Republicans - which means that a debate "win" might not help her at all.

Smart takes from both, as usual.