So, my 'friend' upgraded to iLife '08, and iDVD bounces in the dock a couple of times, flashes the startup splash screen at me for a millisecond, then disappears. Apparently, there are other victims:

iDVD '08: iDVD may unexpectedly quit when opened (http://docs.info.apple.com/article.html?artnum=306064)

iDVD '08: iDVD may unexpectedly quit when opened
Issue or symptom

If iDVD '08 is closed immediately after the startup screen when the application is opened for the first time, opening the application a second time may cause it to unexpectedly quit.

Affected products:

iDVD '08
Solution

To resolve the issue:

In Finder, drag the following folder and file to the trash:
~/Library/Application Support/iDVD/Installed Themes and
~/Library/Caches/com.apple.idvd
Reopen iDVD '08, create a new project and wait for the Updating themes progress bar to complete before quitting the application again. You only need to do this once.
This document will be updated as more information becomes available.

Does anyone have a fix that actually works?

The ones we found do not.

iDVD won't open - MacNN Forums (http://forums.macnn.com/90/mac-os-x/344843/idvd-wont-open/)
iDVD '08 Fails to launch - Mac Forums (http://forums.macrumors.com/showthread.php?t=340535)
iDVD '08 crashes - Mac Forums (http://forums.macrumors.com/showthread.php?t=339152)
MacMost - Apple fix for iDVD '08 'crash on launch' problem (http://macmost.com/story.php?title=Apple-fix-iDVD-08-crash-on-launch-problem)
etc.

Black MacBookCD2.0 Ghz 2GB RAM OSX 10.4.10

All of it worked fine for me. Even iWeb upgraded my Domain file flawlessly.
I actually like iMovie, but the upgrade leaves your old iMovie installation intact. I don't know why there was such an issue about downloading a copy from Apple. Nice to play with both versions.
iDVD is much faster than the old version and has some nice themes.
I wasn't crazy about the iPhoto update until I figured out how to stick with photos and not events. The upgrade automatically put my thousands of pictures into groups by date, which doesn't mean separate events. It will take me weeks to sort that mess out. Thankfully I keep a full backup on hand.
I wonder why it works fine for some and not so fine for others?

What about third party extensions (APE enhancer, default folder, etc.) I heard that some theme enhancers were messing up iPhoto 7.

I'm on a 24inch iMac 2.16/7600GT

I had this same problem and this is how I solved it.

Run Onyx (repair permissions)
Dump iDVD permissions
restart
Reinstall iDVD (only install iDVD not the other stuff)
repair permissions
restart

should work...

Best of luck.

Thanks! I finally had a chance/the inclination to perform these varied steps, and now iDVD works.

I had this same problem and this is how I solved it.

Run Onyx (repair permissions)
Dump iDVD permissions
restart
Reinstall iDVD (only install iDVD not the other stuff)
repair permissions
restart

should work...

Best of luck.

I wasn't crazy about the iPhoto update until I figured out how to stick with photos and not events.

Could you please explain how you did this.. Thanks.