I thought my MBP was sluggish after 10.6.6 update, with longer boot up and shut down times. So, I backed up my files and did a clean reinstall, used the 10.6.6 combo update and reinstalled my apps and files and everything is now as smooth as before. As a matter of fact, iPhoto 11 and iMovie 11 seem a little bit snappier (may be my imagination, though).