Well I finally used the X5 to tow my boat on a long trip, mostly highway but some unpaved roads on the last 10km to the lake we were staying at.
My boat only weighs just over 1100kg, and the trailer doesnt have any brakes. The X5 tows it perfectly, with no shortage of power or stopping power. We passed several other people towing their boats. Why do people insist on towing with such gutless vehicles?
On the unpaved roads the X5 is a bit bumpy, and the ABS was a bit sensitive, but the large tyres are not really designed for gravel. Im happy to sacrifice offroad comfort for onroad handling :-)
Fuel consumption was 16mpg, but highway speeds were around 100km, and we had to climb alot of hills. All in all a good trip.