I just updated my TidBITS article with two new pieces of information about what's changed in iMovie '09 8.0.1. I'm running short on time today, so I'll just paste the relevant sections here (green indicates new material).
Interlacing Bug Fixed -- Here's something I think Apple would want to trumpet loudly. It fixed a bug where 1080i (interlaced) footage would appear combed when exported to QuickTime or iDVD. Prior to the fix, getting a clean HD picture required that you process the footage in other applications after exporting. Now, the bug is fixed.
But there's an interesting side note to exporting interlaced footage. If you export at 1920 x 1080 to AIC (Apple Intermediate Codec) or Apple ProRes format, and you haven't performed any operations which scale, crop, or otherwise change the size or speed of any of your clips, then interlaced 1920 x 1080 footage is passed through unchanged.
Transitions in Split Clips -- If you split a clip and then put a transition at the split, the two halves of the clip now overlap each other (maintaining overall duration). This allows you to, for example, add a video effect to one portion of a clip and use a cross dissolve to fade the effect in or out.
I also added Get Lat Lon as a source for finding GPS coordinates, after a reader recommended it. Same service, less ad gunk than iTouchmap.