I guess you were asking if I was in love with M7? I have two older (4 years) that I know for sure are M7, and they seem to be okay so far, no leaning like others have noticed.
I thought I had bought two other M7 trees that same year, but they might be M111 because they have significant burr knots. Either way, they seem to be pretty sturdy trees.
I just have a bunch of grafted M7’s because I preferred them over the G202 and M111 they also offered. I had two G202 trees, one is doing fine, the other croaked this year, so I’m not too keen on those. And I didn’t want M111 because they take too long to get going.
If there’s a rootstock I really like, it would be G30, I have three trees, and they are both precocious and vigorous. Two bore fruit after two years, and the other after four, although it had a lot of blossoms killed in recent freezes.