On the issue of diesel performance, fuel economy is it worth it? I think the point made by BMW in this piece from Edmunds (at the LA Auto Show) is interesting:

"The 2009 X5 xDrive35d, er, diesel X5, comes in at $52,025, but since the base X5 lacks the company's twin-turbo gasoline inline-6, the price jump is easier to swallow. BMW says the diesel X5 will hit 60 mph in 6.8 seconds -- as quick as the V8 X5. Rated at 19 city/26 highway, it's vastly more efficient than any other BMW X5 past or present."

So for those opting for the 4.8, I say this. You get a vehicle (35d) that will all but match the 4.8 in acceleration and best the fuel economy by 40%+ on an mpg basis. After you adjust for cost, you'll still be 20% ahead, with a vehicle that costs $7,000CAD less than the 4.8. That's why they are going to sell and have better residuals than the 4.8. It get my provisional (until I drive it) vote.