Just spent most of an hour roaming the Internet to see who says what about Obama's Afghanistan speech. Here's a quick response, then I need to go do more important things.
The decision itself - add forces, hope they'll do well enough to be able to leave- is OK. I read the McChrystal Report a few months ago, and he mostly convinced me; it seems he mostly convinced the president, too. The advantage the decision makers have over me is that they've got oodles of data I don't have; the disadvantage they've got is that they've got to make the real decisions. What we all have in common is not knowing how things will turn out. Ah, and we've got the common enemy of anti-human Islamists; there's that, too.
Here's hoping the historians of the future mostly tag Obama's decision as wise and successful.