Hi Dancing Letters: It's a bit of a slice matching the narration to the transitions. I'm still working on getting it right, but here's what I did, or am still doing until I figure out a better way.
I do the slideshow first. Then I read the script and time myself on each page as to how long it takes to read the script for each slide.
I then set the transitions to a bit longer.
The problem is, when you export to Quicktime the transition time changes. However, I see that you can set the slide time and transition time when you export, so what I'm trying now is to set a fixed time for each slide that matches the option in the export to quicktime menu, ie., 5 seconds, and the build at 2 seconds. That way I know what I'm working with. I try to keep the script about 4 seconds just for a bit of leaway.
So when I record the audio in GB, I know I have 4 seconds for each page/slide.
Also, I record in GB without looking at the Keynote presentation. That way I can add a background music track as well as the voice over. I then select the recording I made in the inspector and add it to the K presentation.
It's not working perfectly, and there has to be a better way. I'm looking at Aperture right now as it seems to be more flexible than Keynote.
I'm signing off now but will check back later to see if you have a better idea or method. Perhaps someone else will come along, as well, to help us out.