Smoother, I was loaned an R1200 thingy, when I reved the bike it leaned over a bit, nothing like that with the 800 twin, probably need a few more revs to shift it though.
You shouldnt have a problem with weight coming from the 1200, but remember if your trigger happy on a loose surface, it doesn't have traction control.
You'll want to buy one after you have ridden it, tell us how you get on
if so I would expect you to find it a bit top heavy off road- they seem to handle better on the dirt with a full fuel tank, you may like the fuel consumption tho, 17litres= aprrox 230-250miles, around 65mpg banging around, low 50's on offroad days
if you havent/hadn't had a sauce, dunno, but the front 21" may make it feel a little odd on the road.
I took their demo out a few weeks back too. Much smoother, less weather protection & sounds brilliant with the stock can! But I was glad to get back on the GS at the end of the ride;-)