I just saw this thread and opened FCE4 and Imovie9. I was able to import a screen capture from Quicktime into imovie but not into FCE4. That sucks and doesnt make any sense to me.
Is the QT X issues due to the Quicktime Player and the QT X API? Just looking at the Ars Technica review article, it seems the issues are through the changes Apple's been making.
I was having the same problem yesterday, spent much of the day experimenting, poor quality video when QT screen recording taken into FCPX.
This morning I did a software update and there were two, both QT/FCP related, including a codec update. (new iMac running Lion)
It seems to have made a difference (or I didn't do things right yesterday!)
Record High Qual in QT then import into FCPX and put into timeline
Scrub the clip and it looks fine. Play the clip and it looks blurred BUT
Export the clip from FCPX to YouTube (which is what I want to do to share training videos with my customers) using Large 540p and the result is very good - more than acceptable quality.
There may be other settings that work, I have only tried that one.