I don’t work with HD but I can offer these two facts:
1) I’ve gotten good results going directly from and SD project
2) I’ve heard that it works just as well with HD
So no, I don’t have any experience with it but I think it’s worth your time to try it!
At that lenght I’d suggest a CBR compression around 6.0 (just a guess, I don’t know your content…be prepared to try it again if it’s too big or too small).
You should open up the “90-MIN Best 16×9” preset that’s in there and duplicate it. Look at the settings and see what they are (I can’t check where I am). I’d start with that one and modify it. Be sure to watch for any of the widescreen or anamorphic checkboxes. (That may all be taken care of in DVD Studio Pro…but check here, just in case.)
You can also make your AC3 audio files from here too. The “Dolby 2.0” setting does that.