Macworld has posted their review of iMovie '08, written by Mike Curtis of HD for Indies. (I was originally tapped to write the review, but I had to back out; my plate is overflowing already, and I wouldn't have had the time to review iMovie '08 fully given that it's now a completely new program.) Mike gives it three and a half mice, and does a good job of accentuating what's good about this release while acknowledging the consternation that many iMovie HD users are feeling.
iMovie ’08 is ideal for consumers who want quick and easy editing for a variety of video formats and the ability to three-click publish to YouTube or a .Mac Gallery. For speed and convenience of browsing, simple editing, and sharing, nothing in its class can touch it. While great for its intended audience, the video-quality issues and editing limitations make this a poor option for users with heavier editing demands. If you want better quality video processing for DV or HDV footage or third-party plug-ins, or if you need any of the other now-missing features, stick with iMovie HD 6.