Not a big fan of Alexander Russo, but he does a good job of critically picking apart TFA in a recent post over at The Huffington Post. My Opinion is that it's a lot of well-meaning people who have great academe credentials but that they're not around long enough to make a lasting impact.
More recently, the underlying question of whether TFA members stay around long enough to make a real difference has re-emerged. TFA members are only asked to stay in the classroom for two years, far too brief a time to make much of a difference to anyone besides the individual students they teach. A substantial number don't make much past that. In 2005, The Onion parodied the situation: "TFA Chews Up, Spits Out Another Ethnic-Studies Major."