You must be the exception...
I have talked to over a dozen people that use 10.6 and iMovie 06 successfully.
I do believe that there is an issue with some users, hopefully these issues will be discovered and everyone with iMovie 06 can start using snow leopard.
Reading the posts here is not a good way gauge the compatibility of iMovie 06 and 10.6 because (mostly) only those with problems will post (similar to the way you will find a higher percentage of sick people at a hospital).
The best course of action for those with problems with iMovie 06 and 10.6 is to send feedback to Apple. Apple is well aware of the many people using iMovie 06. (Most I know also have iLife 09.)
Feedback for Snow Leopard
http://www.apple.com/feedback/macosx.html
Feedback for imovie (say you have iMovie 06)
http://www.apple.com/feedback/imovie.html
Pass on your concerns to Apple, be nice, be polite, be HONEST.
Apple does listen to it's customers and respond.
http://www.apple.com/contact/