Thanks for all of the replies guys!

I am DEFINITELY interested in the diesel, since I like the idea of owning a diesel, for the torque and fuel economy. The only drawback for that is the dang-near prohibitive cost of diesel fuel here in Washington. Diesel costs, on average, about 90 cents per gallon more than premium, and I don't think the savings in fuel mileage will matter much compared to the extra price of fuel, plus the additional cost of the vehicle itself. If I still lived in Texas, on the other hand, where diesel is only slightly more expensive than premium, I might consider it a little harder.

The N52, from what I have read, produces right around 270 HP, which is more than the M54 that my current X5 produces. I imagine that it translates to slightly better city performance and highway merging/passing situations. Is the V8 significantly faster, with the 350 HP that it produces? Not that I want a speed demon of a car, but it would be nice to have the extra power when needed...