I had a ton of green screens to do and was dissatisfied with chromakeyers that came with FCP7. Found a really good plug-in from DVGarage. It's called DVmatte pro and it's an excellent keyer. Very easy to use. Worked great on video that was shot 4:2:0 and we know how tough that is to key! Anyway well worth the $200 if you're doing a lot of green screen.