Ben Affleck is a good actor and a better director. He along with Matt Damon are also smart actors, which is uncommon among "movie stars". They went into a deal with Harvey Weinstein and Miramax way back when where they were promised "Good Will Hunting" (which they apparently had some help with) would be pushed and they would be made into stars if they signed contracts with Miramax to star in X number of films (the same way Nick Cage is obligated to do tons of crappy disney movies), hence why Affleck was in a lot of bad movies like "Bounce".
I really like Ben Affleck's directorial work... he focuses on character driven drama... that's a rarity these days. He's a solid actor... he's always looked a bit "off" because he's a big dude (6'3" or something when most male movie stars are in the 5'9" range) and he got a bit caught up in the celebrity... but he really cares about movies and it shows.