Do they play nice? Are they completely compatible, or are there problems with some functions not working?

Info: Preliminary Final Cut Pro X Considerations : CineForm Support (http://support.cineform.com/entries/20328292-preliminary-final-cut-pro-x-considerations)

Thanks David, looks like I'll stick with FCP 7 for now because choppy playback in 3D is a horrible thing to endure. I hope that CF posts any updates that improve Neo3D performance on FCP X in the future.

We find to opposite, FCP X is a little faster. However it does some stupid things and tries to load every compressed frame into memory (notice the disk thrashing on project load.) So the first playback can be poor, but then it get better, once FCP-X has cached everything. Nothing we can do to change its default behavior, so look for more Apple updates (ask for some cache controls.)