Well, without reading what the professionals have to say, I'm going to call this a marginal strategic victory for Obama. Admittedly I've already declared Romney toast, but this does nothing to change my perception.
Not just for the prevent defense. Obviously Romney needs a major shakeup and he didn't get it, and time is running out.
Romney looked pretty solid on stage. No obvious screwups. Decently aggressive without being rabid. Seemed to be in command of the subject material. He also scored well in terms of reiterating his attack on Obama, even if it included repeated references to patent nonsense (e.g., "stole $716B from Medicare).
However... he wasted a lot of time on subjects that are low-return for him, if not actually dangerous. Example, the repeated attacks on Obamacare (now that Obama has embraced the name, I'll stop referring to ACA as such as well) will. not. help. He's already got the folks on his side who are worried about it, and his strongest demographic -- seniors -- already hesitate to trust him on the related subject of Medicare. On the minus side, he can appear to be caving on the provisions of Obamacare, which should scare his base, but won't win any converts elsewhere. Worst of all, it forces him to thread the needle between Obamacare and the Massachusetts plan (Romney has not embraced the term "Romneycare," gee, I wonder why). The longer he stays in those waters, the more risk he takes.
Similar for education. You and I and everyone studying this already knows his tax and budget plans either ravage federal education funding, or are total fantasy (I choose column B), but most folks watching won't know or won't care. What they hear is a mixture of "education for everyone" and "kill wasteful evil federal government," and there's no clear message. Muddled messages are a minefield -- is he actually thinking of continuing support for teacher's unions? the hard right will wonder -- and I give him credit for dancing out of it, dropping just enough carefully coded language about education vouchers to escape intact, but that's a fight he shouldn't ever have gotten into in the first place. He has no way to win on that issue.
Romney laid down his attacks efficiently, but they're all old attacks. They haven't won the race for him thus far, and they won't in the future. Obama certainly started slow and didn't throw too many punches, but he doesn't have to.
What it comes down to is this: Did Romney gain anything from this debate he can use later? And the answer is a resounding "no." Obama on the other hand teased several details and new positions and promises out of Romney that we haven't heard before, all of them things that can be turned to an advantage. Scarily, he did so despite being even more wooden than usual on stage. But I wouldn't call that an unforced error on Romney's part, rather I see this as the logical result of Obama's strategy. His record is public and his defenses are limited. Yet he still manages to give Romney more and more rope, and those knots have tightened marvellously since the DNC.
The one clear win for Romney is that he won the battle of expectations. Turns out all the hedging and backpedaling and underselling both campaigns did was spot on after all. Romney did win the optical battle, clearly holding his own against the President so long as we ignore the actual words spoken (most of which admittedly were fluff on both sides, as always). But I don't think this is enough to make much difference. At the end of the day this will go down in history as a forgotten debate, its only strategic value being a sort of spoiler for Romney's continuing roll-out of his forever malleable policies, and that is blow that he surely cannot afford.