I have a 2011 S5 which I just picked up a month ago and was able to drive for 2 weeks while I was home on R&R, and I noticed the same thing. It had 23 miles on it when I picked it up and it now has roughly 1600 mile on it from a road trip I took while I was home and I'm pretty sure I noticed the jerking/lag on a fairly regular basis. I'm back in Afghanistan now so I'm not in any position to call Audi, but I plan on taking it in when I get back and having this checked out.
"Don't Talk About It, Be About It"
2011 Audi S5 Prestige, Phantom Black, Black Silk Napa Leather, Stainless Steal/Piano Black, Bang & Olufsen, Nav + 3G MMI, Audi Drive Select Package, Titanium Package, Clear Bra, Tint, AWE Touring Edition Exhaust System with Diamond Black Tips