I'm 6'2"ish (mostly legs) and about 215 lbs, and I'm very comfortable on my '08 S3. It's a bit taller and longer than my '97 Buell Lightning that I upgraded from. Haven't put any luggage on it (just a small tank bag), and the lady rides her own bike, so haven't ridden two up either.
And a word from the not-so-wise... Don't practice your wheelies right after eating a big burrito. I romped on the gas, and the tank nailed me square in the belly, and then when I dumped the throttle I dropped my belly back down on the tank. Felt like blowing chunks afterward. Not very graceful.