Took delivery of my X3 28i in September. 700 miles. There is some lag but nothing that is too different from my 2006 330i and 2008 328i.
If you've driven BMW's before in the last 5-6 years, this lag shoudn't be a surprise. In fact, you should also know that after a few hundred miles the transmission will learn your pedal behavior and auto-correct itself.
Quit complaining. You all should have test driven the car before you bought it. If you didn't like the acceleration then, you shouldn't have bought the car.