For performance in a SUV, there is nothing better than the BMW. Gas mileage is as expected for a high performance SUV (averaging between 16-17). BMW needs to improve the electronics of the vehicle. Mine has had window issues and the navigation system is spotty at best. The premium seat package is worth it, some the most comfortable I have had. Be aware that the run flat tire will cost you serious money when it comes time to replace them and be HP tires, they don't last as long as an average tire. The do stick o the road and give you a very confident ride. While sticker shock may keep you from considering the BMW, once you drive one you will get hooked. I saved a significant amount getting a 2008 rather than an 2009/2010.
The 2008 BMW X5 feels very solid and well built. It has about the same driver leg room (I'm 6-4) as a much bigger SUV such as a Lincoln Navigator or Ford Expedition but handles and drives far better. With the 3.0 in-line six, perfomance is very good, especially in Sport mode. The V8 version is even better. So far, I am averaging 21.1 mpg with a mix of in-town and highway driving. Overall, I am very happy with the X5.
I love this SUV. It is big enough without being obnoxious. The third row seats are easy to operate, My 6 & 8 years can operate them by themselves. It is a smooth ride, handles like a little car on the mountain roads and the sport package is just great. The only reason I gave it a 4 overall instead of a 5 is because the USB port is very hard to use. Theres a little cover and you have to insert it at just the right angle.... It's more effort than it should take. And the Sport equipment cover is not easy to store in the car, when you have to use the 3rd row seats. This is an 08 model, so I am guessing these issues are moot and have been modified for the newer models. Overall GREAT vehicle.