I am picking up my 07 X5 next week and trading in my 2005 Porsche Cayenne Turbo. First things first, the Cayenne Turbo is a very quick car. It has a great exaust note as well as the option to change ride height and comfort settings (sport, normal and comfort). A few problems- the car is very bouncy in IMO, but takes turns relatively smoothly. The headlights are very bright, and my friend has had some people flash him because they thought his brights were on. The worst about it is the economics are really bad. The seatbelt buckle is tucked away, the air conditioning is a pain, the stalkers are cheap, and the passengers electric seat stopped working, the heated seat buttons are ripped from a VW jetta and auto headlights are not standard. The ride on the highway is hard to beat, but city traffic did not please me too much. The BMW's interior is alot more refined, with more packages available instead of stand alone options like the Porsche. Since I have not taken the car for a real spin I cannot comment on the ride on the X5. The best thing to do is to test drive both of them...test drives are free :-). Hope this helps.