I'm having the same problem with my April 2008 Build E70 4.8i.
From a dead stop it stutters, hiccoughs and then surges. It is nearly impossible to modulate the throttle from a stop with out jerking my passenger's heads back and forth. Although, unlike some of the other posters, once it gets going, I don't find it is slugish.
I mentioned it to my SA last time I was at the shop and he said that's just the way the X5 drives. You can guess my response, since this is a $72K SUV that is more difficult accelerate smoothly in than my M3.
I wish we all could collaborate to convince BMW this problem is real.
Supercharged Mach 5
The Original M5