I'm new to burning DVD's. I've successfully made one DVD, the type that would play on a regular DVD player. Took tons of time adjusting movie files to just the right .mov format and it appears that I cannot have more than two hours of content on the DVD. And then with the Dual 800 mhz G4 I have takes a lloooonnggg time to encrypt. (about an hour)
Now a DVD-R as storage I can fit half a season of a TV show with low compression. I love DVD-R's and making video DVD's. 
But let me get this straight... iDVD can only make DVD's where the CONTENT take up less than 2 hours right?
If so.. what a waste!
I think newer versions have better limits. I once made a DVD of the Beatles movie Help! from a VHS copy I had, and I had to cut pieces from the movie to make it fit on the DVD and the film is relatively short. That was a few years ago, and I know since then they extended how long a movie you can burn.