I traded in my '02 X5 4.4i for an '06 530xiT with N52 engine. While I appreciate the N52 for its fuel efficiency (26-27 MPG open road), tractibility, and overall superb manners, I sadly miss the low end grunt of a V8. Sitting in stop and go traffic, my 530 sports wagon feels alot bigger than my X5, despite weighing 1000 lbs less, simply because the N52 engine can't spool up fast enough to dive into a lane opening from a dead stop. That being said, I can imagine the condition being alot worse with an X5 equipped with the straight 6. The N52 engine performs best at 4000 rpm or higher and does quite splendidly on the open highway with the Steptronic set in sports mode.

That being said, I'd opt for the V8 in an X5 and sacrifice any creature comforts that are expendable . It's a beast of a car in terms of curb weight; it is probably best enjoyed when equipped with a beast of an engine.

Knock off the ventilated seats and HUD. Leave off the rear shades and get the a darker tint of privacy is what you want. Although others might disagree, I'd get rid of the comfort access which I consider a nuisance after 3 weeks of experience with it. IMHO, get the V8. It's worth it.