You might want to read this link from AppleInsider before changing over from iMovie06 to the new iMovie08. It appears that some features you may have grown used to in the ’06 version are no longer available. The post at AppleInsider makes it sound like Apple went for simple almost assuming the most common interest of iMovie users was to post something to YouTube.
I can’t say I have had the opportunity to work with the new product yet, but I would be concerned that movies would lack chapters. Since it might be time to load software into school labs for the Fall, those considering the new version of iLife might want to take a little time to investigate this issue.