The new Jeep GC is a very nice vehicle. I test drove one before getting my X5d, and later had one as a rental. Very solid, German feel; clear evidence of partnership with Mercedes. And good value. But I've had Jeeps before, and I don't think they have come far from a reliability standpoint (not that BMWs are the most reliable).

A note on your experience with lag in the X5d. Be aware that it will start in 2nd gear if you are not in 'sport' mode, and not heavy on the throttle off the line. When it starts in 1st, there is no noticeable turbo lag.

That said, if you are looking for an SUV with German feel that can tow, also check out the new Touareg diesel. It has a much higher tow rating than the X5 (7,700lbs?), with comparable power and better fuel economy due to its more modern transmission (8 speed, I believe). Slightly more bang for the buck as well in terms of features in the price range you are looking for. That would be my choice over a used X5.