Of course Clooney and Pitt have great on screen chemistry. The story is funny, and cute and enjoyable. It's a not a buddy, buddy flick. The plot does lag and they have to catch you up in the end which is lazy writing, but it's certainly not formulimatic. The action also lags a bit at times but there is enough and well designed but it's not an action movie.
This is a nice movie, the type you used to rent on a Saturday night because it was good, but a little safe.
Ultimately, this is worth the popcorn.