The staff stand bag is 6.0 lbs. and the lightweight stand bag is 5.2 lbs. These both seem pretty reasonable as far as weight is concerned.
I think the biggest difference will be all the stuff people will cram into their bag. 0.8 lbs is barely anything, but once you stuff the extra pockets with extra stuff, it'll be a lot heavier. The lightweight cart bag is also 6 lbs, but I guarantee if you took the average cart bag and the average stand bag off the course and weighed them, the cart bag is going to be heavier when fully loaded.
I guess what I'm getting at, if you're that worried about weight, focus more on what's in your bag than the weight of the bag. Now with that said, good for Titleist to offer such a great and full featured bag while keeping the weight low.