As I understand it, after effects has some pretty sweet keying tools, or at least better than Premier. I've played with it and have gotten some good results as dictated by the preview. However, my question is with exporting. I am doing a documentary and am using interviews with a greenscreen background, but when I try to export the final product, it always comes out jumpy...Why is this?

What do you mean by 'jumpy'? Also, what compression settings (if any) are ya using? I normally export uncompressed unless I'm previewing something :)

Maybe you got lower/upper field settings mixed up.

You could also be rendering at draft quality, which would make everything appear quite a bit more blocky than it otherwise would. Coupled with out of order fields would probably result in quite a crappy looking video.

How are you playing back the exported video; how is it jumpy? Often if you have a large file and you're trying to play it back in something like Windows Media it will appear to skip as if you're playing it off a CD because WiMP can't buffer huge files.