Andrea, I guess that you are editing at 1080p (@29.97fps ?) and your source videos are at 1080p. I can not compare your powerful i7 Notebook with my poor DualCore Notebook, but I noticed that, when I use transitions, it is better, on my system,to set Video driver on X11 and "use direct x11 render if possible" in Preferences. Have you tryed, just for testing? IgorBeg