Ulead DVD Workshop 2 was easily one of the best programs, made by a now-defunct company. It's essentially abandonware. PM me about it. You can do some very advanced things, yet the GUI is fairly intuitive and makes the program easy to use.
There more info here:
http://www.digitalFAQ.com/forum/dvd-menus/
I've been asked to make a text/image guide for it, and I'll be doing just that in a few months at most.
The other option is TMPGEnc Authoring Works. The menus are not as good as DVDWS, but much better than Nero.