just to quickly let you all know this isn't about smoothing out camera jitter!
I have 2 HD prores mov files in quicktime that play fine. I've converted them both to prores lt and imported into fcp, to find that the image is a little jittery. It doesn't seem to play back as smoothly in fcp as it does in quicktime - which i'd be fine with if it went back to being smooth on export - but it doesn't!
The biggest problem is with my 7d footage, which was shot at 50fps and i've slowed it down in cinema tools to 25fps. Again, when i play this as the converted mov quicktime, it's quite smooth - but when put into fcp, it starts to jitter, and the problem is now there on export.
The other file is 16mm footage, which is also fine as a tk'd mov quicktime, but when played back in fcp (as prores LT) some of the frames seem to get caught.