Here is a very brief opinion on owning a second hand BMW R1150R. Some of the issues I had and other things I wished I knew when buying one.

+ The engine is understressed and can outlive many of the other components.
+ Nice luggage, very good for 2 up riding.
+ Torquey engine, shaft drive means no chain to oil.
+ Better braking than anything out there, with only 1 finger.
+ Still a true boxer and the only one I know of still in production.

Heavy bikes and perhaps overly complex, these are not the BMW boxers of old.
Linked brakes, iABS and a lot of servos are potential issues with old bikes that were not properly cared for.
Dubious quality plastic used in places where they should have put metal, especially since we are dealing with a "premium brand".
Definitely not a bike to own second hand for the financially or mechanically challenged.