I'm really just thrilled that Donald Trump is (a) apparently serious about running for President under the GOP banner and (b) is going the full birther (and not just because he can't even manage to grandstand on it effectively). Trump is not a serious figure, but he has enough money to at least command attention in a GOP primary (and enough delusion to actually throw it away). Which means birtherism stays in the news as Republicans debate, and the Party can't dodge that it's a thing for them.
Anything that emphasizes to America that, hey, we're dealing with a Party that collectively has gone off the rails, is something good for not just Obama, but that entire Democratic Party in 2012.
UPDATE: Dave Weigel basically concurs.