I believe in doing what makes you happy as long as it doesn't hurt others so if XMs make you happy fine BUT, I don't think real car people buy those. I know Dr. Kay loves it, but I think they are bunk and don't make any sense whatsoever. You start with the tallest and heaviest platform, add a ton of more weight to power them and stop them. Chop the back to make the semi aerodynamic so there is no cargo space and you end up with a 5000 lb monstrosity that does nothing well. It's not practical, not economical, can't carry much more than a regular 5 series, squanders gas like it was the 1930s and is not a serious car. Yes they are cool in a Tonka truck sorta way, no doubt, but not a real car guy car.
Finally, those that think that run flats are for serious car people, why are M cars the only cars that don't come with them standard? You think the M engineers just figured non-runflats are cheaper so they put those on the M cars? No sir, there is a performance reason for them, so real car guys today, don't want run-flats. Maybe soon they will be as good, but today, non-runflats and a spare is still the way to go for people that like to drive hard and venture past the 200 mile runflat zone.
I remember the first car and driver review of the 335i. BMW gave CD a 335i somewhere in Austria. They had a mishap and got a flat. There was no one for hundreds of miles that stocked the tire so BMW flew one in by helicopter. That won't happen for us.