I have had my 04 X for 3 years and I have spent $8000AUD on maintenance, $3000 were repairs due to poor build quality rather than wear and tear and I also had a tranny rebuild which praise the lord was covered by warranty. I also have faulty side mirrors which have already been replaced once under warranty, and need to be again to the tune of $1000. I also have problems with sunroof but Im not bothering spending an arm and a leg on repairing sub par tech which breaks quickly.
My car is now burning oil, fingers crossed on that one. My boot rattles constantly. Power steering oil is leaking. My cluster is now unevenly lit being very dull in some spots and really bright in another and I am leaking power steering fluid. Unfortunately in my experience the mechanics have a replace rather than repair policy, or replace rather than diagnose.

My car has been well treated and was purchased with well under 100k km and was bmw approved.

some common issues tmk:

Cv boots
Transmission Issues
Excessive oil consumption
Air suspension
Rough idle/start, intermediate levers
Cooling system
side mirrors
Rear tail light connections melt
Squeaks and rattles abound
Clusters issues
and the list goes on....

Don't get me wrong, I love this car...but Im being honest as requested. I'm hoping this car lasts another 5 years without anything too major and by that time I will either buy a porsche cayenne turbo or an Infiniti suv if they are any good (not out here yet). My experience hasn't been great so naturally I'm going to shop around and experience other brands as I'm not old or brand loyal.
Running costs are critical to one working out whether they can afford something, its a rich persons car that comes with rich persons bills!