Play 2 is probably slower than Play 1 in development mode at present. This may change in the future, but you only need it to be fast enough to reload the page without waiting, so there's no reason to run ab against it. If you run it in production mode, then I believe Play 2 is astoundingly fast.
I had so many problems due to bytecode enhancement throwing raging ClassCastExceptions that I'll not even try version 2.
From now, my new projects are in JEE6.
Play 2 is not using that "magic" anymore, so you won't hit that problem (which, on the other hand, wasn't 'too' common).