I don't know what others have experienced, but my iBook is having trouble rendering things in both iMovie and iPhoto. In iMovie, the Ken Burns effect (so cool otherwise) is choppy, even after rendering everything. In iPhoto, I cannot render the slideshow dissolves in Millions of Colors smoothly. I was able to do this in iPhoto 1. The system specs are in my sig.
I think these issues have to do with my graphics card (only 8MB), but any help would be appreciated.