Overall, I like the new iMovie, however one feature I do not like is how the Ken Burns Effect automatically starts rendering when you add photos to the timeline (I certainly don't want to use this effect on every photo). After playing with iMovie for an hour or two, I discovered by accident that if I press the Escape key (esc) immediately after I've added photos to the timeline, they will cease to render and will just be still clips.
Be careful though, iMovie will become almost dead when adding many photos to the timeline. I added 114 photos and it took over six minutes just to add. If anyone else can find a way to disable the auto-rendering of KBE, please post a comment here.
[Editor's note: This is clearly a major annoyance in an otherwise great upgrade. I use iMovie a lot to put together my own slide shows, and I definitely don't want the KBE on every slide. The escape workaround is a nice one, but it would be even nicer to have an on/off switch or something similar...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030204065235938