I am curious how the GH1 is for blue/green screen work? Does it have a sampling issue like typical video cameras? Thanks.

It uses 4:2:0 color sampling, the same as HDV and PAL DV.

You can download a greenscreen clip from the GH1 (and several other cameras) and try the keying for yourself:
The Great Chroma Key Smackdown - DVXuser.com -- The online community for filmmaking (http://www.dvxuser.com/V6/showthread.php?t=190061)

Thanks Barry. I'll work with it later today and see what I can do.

I just got my Gh1 two days ago and wondered the same thing. Shot a couple short, simple green screen clips and they seemed to key wonderfully. Surprisingly well. But I didn't actually export them to see the final product, but I will be here soon.

I should mention I'm using After Effects CS3 Keylight Plugin.