I have a may 2010 build 2011 50i. I have experienced no such problems and I am 25k into her. I did have a sensor replaced in my rear brake. Lame but not a big deal to me, no cost naturally.
The car is insanely enjoyable. A much more powerful version of my last x5, which was no slouch itself
Get one. Yesterday. You will not be dissatisfied. Coming from a 30 to the 50i you will be laughing at the pick up.