But doesn't all of this make all of you who have kids wonder how YOU are going to be as a MIL (or FIL)? If I think that my son and his wife are making a stupid decision, will I be able to keep my mouth shut?
I think all parents are entitled to their opinion. I certainly never expected my parents, nor DH´s for that matter, to stop having opinions on our decisions just because we moved out. It´s more about what you say and how you say it.
I also feel it´s important for parents on both sides to realize that most decisions are joint decisions, made by both partners, nut just the evil DIL or SIL. And although most decisions are joint decisions, there will always be decisions made by only 1 person and parents need to respect that as well. To have a successful marriage you must compromise, which usually means that at one point or another either wife or husband has to "back out".
my husband, and I recognize how lucky I am to be married to such a wonderful man.
Some of the stories I read here about in- laws are atrocious. I can see why people would say "It's them or me". I could never sit by and watch my spouse be treated poorly by others, family or not

Never did anything to her. In fact I tried to encourage a relationship between her and Dh. Didn't work out so well. At FIL's funeral I introduced our son to MIL. SHe has NEVER seen him other then in photos someone gave her without our permission. (Taking pics of your own kids or all of them playing together and showing her was one thing, but this person specifically took pics of DS for her.) DH refused to introduce DS and was irritated she even showed up, so I did it. However I am still a bad person! Only no one can seem to tell me WHY she hates me so.