Another nod for MovieFactory.

I similarly use it for projects from PSG and various other video editors and Other editing packages (even those with buit on DVD authoring ability) however, in its version 6+ it also has editing facility..which you can chose not to use
It can take DVD ready mpeg2 which it will not re-encode in making a DVD
DVD Architect Studio ( From Sony Vegas family) is usually packaged with the Main Program but can be used as a standalone.
I also use MovieWorkshop2 which has sadly not gone beyond ver 2 and does not support Hi def. It is however very slick and is easy to use
Although Nero Vision has editing abilities you can simply use it to author DVDs but it is not nearly as richly featured as UMF