I don't know if this is in the right forum, so I apologize in advance if it's not.

Is it possible to do effective CG at DV resolution? For example green screen work or person rotoscoped/morphed into a tree, 3d designs with live action.

Thanks

For CG, lower resolution makes your life a lot easier because you need less detail (less labour to make things realistic, lower render times).

As far as keying goes, you'd be looking at DV (because it's cheap, and you presumably own a good DV camera) or a format better than it. Some people say betaSP is better because they have better luck than it; if you read Adam Wilt's DV FAQ, he argues DV is just as good as betaSP when implemented properly with chroma smoothing (FCP has such a filter... it's the color smoothing filter; there's also Nattress' G Nicer).

Ultra's demo for their keyer looks really good. It may be a good way to get really good keying results with DV. (Haven't tried it myself, sorry.)

Above DV, you'd be looking at formats which support 4:2:2 or 4:4:4 color sampling.
4:2:2 - DVCPRO50, digibeta
4:4:4 - film --> data, HDCAM SR, Andromeda -modded DVX100, kinetta or other video camera with 4:4:4 output

I'm not aware of any comparison between DV and those formats above, although they'd definitely be helpful and interesting.

2- You still need a decent camera. Some 1CCD consumer cameras have false colors and could potentially give you really poor results compared to better DV cameras.