I only drive in automatic mode.. and never notice a take-off lag (and my other car is a SAAB Turbo, so I know a little about launch-lag). I'd say, for one thing, the longer the has been broken in the smoother it drives. I've never noticed a car to enjoy the benefits of the break-in period as much as the smart.
The only lag I usually notice is when I slow for a turn, so the car shifts down to 2nd, when I'm really going so slowly that it needs to be in 1st.. then I get a shudder, as the car attempts in 2nd to drive till it downshifts into 1st. That's some lag. Otherwise, I think it takes off smoothly.