I have now owned the M5 for 4 months and it is pretty much broken in. I love it! I told myself min miles ~6-8k a year, but I have to drive it everyday! I just get a big smile on my face every time I get into it! Gas mileage update - I have a 25 mile drive to work everyday on a 45mph road w/ about 30 stop lights (that I constantly get caught at). I mostly drive in 400 hp (D1), but I let the 500hp monster go quite frequently (S4)- say 5 times a day (I'm gonna need new tires soon $$). With that, my avg gas mileage is better than when I first got it (see my first review) - 17mpg or ~330-350 miles before I fill it up.
I love the looks that I get. I am normally a fairly laid back guy, who doesn't like the limelight. But you can't avoid it in this car. Whether the person is 15 or 65, man or woman, this car just makes their heads turn! I'm used to getting stared at now! Maybe it's the color - Interlagos Blue!
Head's Up display should be focused at infinity (not 10 feet, or whatever it's set at) in front of your face. I still get a kick out of using it, but I have to re-focus my eyes on the display everytime I look at the display. Wastes about 1 sec, of focus/refocus time. Not bad, but it could be better.