I've been using iMovie 08 quite a bit lately in making music video and video clips.
Stuff that I like:
-Audio fade-out bug fixed. In iMovie HD, whenever I want to do an audio fade-out (during transition, in the end of the video, etc), for whatever reason, iMovie HD frequently chokes and the audio stutter. At first I thought this is only on the project/preview, but the stutter is permanent, included in the final video. Highly annoying. I have yet to have this issue in iMovie 08, and iMovie 08 handles audio fade-outs almost automatically most of the time.
-I love the youtube uploading automation a lot. Makes things much easier and more straightforward.
-Adding and editing the duration of transitions feels easier and more straightforward. Again, iMovie HD sometimes chokes on transitions for whatever reason.
-iMovie 08 doesn't recognize non-native videos (xvid) after importing, even if you cut them using QTpro and have .mov container and/or installed the codec support for Quicktime (ie. perian). I had to export the xvid clips to H.264. A way to promote QTpro? QTpro IS useful in cutting down xvid videos and exporting the clips to H.264, so you don't have to wait iMovie 08 transcoding the whole large xvid video.
Stuff that I missed from iMovie HD:
-Effects! There are TONS more effects and transitions in iMovie HD, even advance effects like faster/slower video speed. iMovie 08 has no advance effects, and only basic transitions.
-Editing texts feels easier and more straightforward in iMovie HD. It's confusing to edit the text in iMovie 08 outside the preset ones.
-Timeline view. One time I want to start working on a video clip in iMovie 08 starting from the end of the backgroud music and working towards the beginning. No can do. iMovie 08 snap the video clips in ascending order from the beginning of the backgroud music, and I can't find a way to snap them to the end of the music. The timeline view of iMovie HD gives more flexibility in creating a project.
In short, I wish Apple improved and fixed the bugs of iMovie HD instead of making iMovie 08. Sure, iMovie 08 makes editing videos more user friendly, but once you get the hang of it, you start feeling limited and wanting more (transitions, effects, timeline view, etc). I guess that's Apple's way to sell Final Cut express/pro.