That is a tough call. I like what Yii said though. If the X5 is anything like the old Mercedes and BMWs of yester-year then it will be around for a long long time. I for one can not get used to the cheaper materials used in average cars. For the same reason I was not able to go from Japanese cars to American. I first got an E class and now an X5, nothing else comes close.
I do worry a LOT about the cost of ownership though.