OK, so we all want the best frame-rate for our preview as we work. But I am finding something odd re the preview quality settings in V8. Which is this:
I have a clip to which I add a Sony sharpen effect. Frame-rate drops from 29 to 14. That's in the Best/Full setting. I change it to Good, same frame-rate. I change it to Preview - same frame-rate. I change it to Draft and zing - it goes to 29.fps. Of course, Draft is too ugly to look at.
So this is quite a stumper to me. I tried other FX, I played with the Ram settings, I played with the multi-thread settings, I made sure properties were set to lower field first. 
I'm using DV .avi files, nothing special.
I have a P4 3.0gh  with 3gb ram. CPU usage is about 65% with the effect on, about 35% with it off.
What is anyone else's experience with these settings?
Thanks
-- 
John