I think the current X5 is pretty good in that regard, especially compared with the first-gen throttle drive by wire models. I had two of those, an E46 330i and an E53 X5 3.0i. Throttle tip-in was really touchy on those, almost as if the sensor would go sleep and take a second to wake up, and god help you if you weren't easing gently into the throttle while waiting for it to wake up.
Anyway, the X5 starts off in 2nd gear in normal mode, so I find the current throttle tip-in to be pretty gentle. Or maybe I'm just used to being really measured with that first 1/2" of throttle travel now.