'09 does offer more features and a few more cool video effects. On the flip side, it presents users with a much more complex workflow requiring careful media management. Luckily there is help for the perplexed.
A former employee of the New Media Center and now adjunct professor in the School of Communications created a series of tutorials not only on iMovie '09, but also on recent versions of iDVD and iPhoto. iLife Fun with Alex is available on iTunes U.
Please note that you will need to have iTunes installed for these tutorials to work. You can download and install it for free here. Clicking on the link above will open a browser window which will then open iTunes.