I've used several different programs and I LOVE VEGAS. It makes me all happy to work with it because so far I have been able to do everything I wanted to do with it. I use it for DV capture, editing and restoring video, editing audio, rendering, converting, just about everything. You can find lots of free plugins on the web if you need them and lots are included with the software. You can overlay text, fade in still images, you can paste in .psd files directly from photoshop with the transparency intact, mix multiple video sources, just about everything you can imagine. It's particularly useful for synching audio. The limitation for me is how well I know how to use the features.
The keyframe functions are a little bitchy to make work, that would be my main complaint. It's also not possible to import an elementary stream like an .mpv file nor can you drag and drop vob or ac3 files. However, you can create system streams from those files in another program and then import. I'm not sure if all programs are like this or just Vegas. Overall, I found Vegas more fun and useful than Adobe Premiere or things like avisynth and less expesnive utilities. The major benefit of Vegas is that it is about as close to a one-stop shop I can think of.
I like DVD-Architect too, but I also use DVD Lab pro depending on the project. The major benefit of DVD Architect is that chapter stops are more accurate, and you can actually see AND listen to your files when you are making chapter marks. You can't do that in DVD Lab Pro and chapter marks are far sloppier. Downside to DVD-Arch is making transparent menu buttons is a major headace. Someone mentioned that it creates needlessly complex menu strucutres - I would say that is more related to the person authoring the DVD or maybe use of an inappropriate template. You can make a disc with no menu, or a menu that only pops up when you hit the menu button, or you can put 100 buttons on a menu page. It's up to you.