I just tied the bow on the latest Breen's Bungalow (the QuickTime tutorial I produce for the CD bundled with newsstand copies of Macworld) and, during the editing process, I finally did the smart thing.
I assembled nearly all of it in iMovie 2.
This particular Bungalow has a lot of scenes (three video clips and over 70 stills and motion screen captures) and editing it in iMovie 3 was painful -- scrolling takes forever and, unlike with iMovie 2, you can apply only one transition at a time.
Here's how I divided the labor between iMovie 3 and 2:
I created the project in iMovie 3, where I captured the video, imported the clips, and placed them on the timeline. I used iMovie 3 for this for a couple of reasons. First of all, when you import a regular ol' QuickTime movie (the kind produced by Ambrosia's Snapz Pro X, for example), iMovie 3 automatically converts it to a file format (DV) that's compatible with iMovie. With iMovie 2, you have to convert these files to DV in QuickTime Pro before you can import them into iMovie. Secondly, when you drag multiple clips from the bin into the timeline with iMovie 3, they appear in the proper order -- the first selected clip to the last. iMovie 2 has a tendency to jumble the order.
Once I completed these operations I saved the project, quit iMovie 3, and opened the project in iMovie 2.
Once there I performed all the operations that iMovie 3 slogs through -- moved clips around, shortened or lengthened stills, and fine-tuned the placement of the voiceover clips. (BTW: One cool feature from iMovie 2 that was lost with the move to v. 3 is the ability to view the location of the playhead in a clip you're editing in the timeline. A faint line appears at this location, making it very easy to adjust the length of stills. I pray that Apple brings this feature back if, as is speculated, a new version of iMovie is released at Macworld Expo.)
With the project nearly complete -- everything cut to length; voiceovers recorded and placed; and titles, transitions, and effects applied -- I saved the project, quit iMovie 2, and opened it once again in iMovie 3 to adjust the volume of the voiceover clips.
Save, export, and done.