While I have had my 2008 M5 since November, I brought it home for the first time this past weekend (the reason for the delay is too long to bother with here). Unbelievably, my wife hates it! She actually said it was "wretched". h: She hates how the SMG shifts (and believe me I was shifting smoothly), she said the interior seemed much cheaper than my previous '04 745Li (despite full leather), she didn't like the seats, it's too noisy, the Nav system sucks, on and on. She even called it baby blue (I have Silverstone II).
I couldn't be happier! I have now found a car that I love that I know she will never want to drive. Man, this car just gives and gives.
No disrespect to your wife but if she "hates" the M5 so much what car does she like?
On the other hand as you mentioned you have no need to worry about her taking the beast out for a run.