I have one fitted to a 2010, which is the same bike as the 2012, so it will fit yours fine.
I had an MRA screen on a CBF600 a few years ago - it was noisy and buffety, but YMMV. I noticed no effect at all from the 'spoiler' thing, and altering it made no discernable difference. I'm 5'11" and wear a Schuberth R1.
The Givi screen is fantastic. In a different league from any screen I have had on any bike. It's as good as the other thread suggests, and BMW should fit them as standard.