Apple posted a new tech note of interest to those who are editing in HDV: Sharing Full Quality HDV from iMovie HD does not export correct aspect ratio (1920 x 1080, 16:9). (Link via Mike at HD for Indies). Here’s an excerpt, but be sure to read the whole page if you’re working with HDV.
After completing your edit of an HDV 1080i widescreen project in iMovie HD 6, you can export a QuickTime movie by choosing Share > QuickTime. You can also choose File > Export and then click the QuickTime icon.
If you choose the Full Quality option from the Compress movie for pop-up menu, you can export a full resolution QuickTime movie for use in iDVD or other applications.
When you import the resulting QuickTime movie into an iDVD project, the video will incorrectly be displayed with a 4:3 aspect ratio (instead of 16:9) when imported to iDVD 6 widescreen project.
By the way, you can keep up with the tech notes that Apple changes at this page, which would really function better as an RSS feed, but oh well.