Not sure if this is treading the line of safe discussion here, but first off I'm not sure if there is a way to copy the digital sound formats (DD, DTS) with a standalone so the best you'll get is Pro-Logic (maybe not even that) and since there aren't dual-layer burners out there if the movie is over 2hrs you'll have to use player compression to squeeze it onto a single layer disc (or use multiple discs) and you know what happens then. I don't have a PC burner so I can't help you there.

it SHOULD be fine as long as you don't explain procedures of backing up the disc.

When I keep the 5.1...it shows up at 5.1 on my receiver and sure sounds like 5.1

Well if PC burners can do the digital tracks that's cool. I'm not sure if I would want a backup if it didn't have those tracks, so I don't recommend standalone burners for that. I use mine mostly for my LD to DVD transfer which most of the time doesn't involve a DD track and an occasional Non-R1 transfer so I can play it on my other players, so I'm happy with my burns.

With CDs, (I dont have a dvd burner so I cant "backup" dvds) I make a backup copy and use that, and safely tuck the original away.

I have had a DVD burner for years (bought the A04 before it hit stores) and have never burned a copy of a released dvd yet.