Maybe I'm crazy. I've been driving 2010 Q7 for the past two weeks and I prefer my MDX. I'd get the 2013 model when my current one dies.
My impressions:
SH-AWD feels much better than Quattro when accelerating at on-ramps
Q7's hood is too long
Brake feel is uneven in the Q7
The 4.7L V8 in the Q7 pulls really well, but seriously thirsty
It's not surprising to see SO many of these new MDXs on the road. I still prefer the older models, though.