Can't resist this one, as a step-daughter.
I wasn't particularly keen on my (now ex-) stepmother. She's not the sort of person I would choose as a close friend, IYSWIM. And she's been a dreadful parent to my half-sister. Although that could be explained by her own nightmarish family background - I guess we are shaped by what we see as children and she's certainly done a whole lot better than her own parents did for her. I think at times she's seen us - certainly my sister - as rivals for the affection of my half-sister. But that's because we've been desperately trying to protect my half-sister from some awful stuff that went on.
We've always been civil, and even had some fun together in the sort of way you might with a colleague you wouldn't choose as a best friend but might find yourself spending time out of the office with. But she's done stuff like insisting on getting in the car with my, my dh and my dad at my wedding (WTF???? I've got a perfectly good mother of my own, thanks very much. And sitting on the top table at my wedding with no invitation when she was already divorced from my dad. And getting in the car with me, dad, dh and my sister at my grandmother's funeral. Again, post-divorce. WTF???)
No idea what she'd say about her experience of step-parenting us, though! Maybe that I was not too bad (since I've never actually let her know I'm not her best mate) but my sister was a nightmare?
My mother v. bitter about ex-step mum, because, for example, my father was defaulting on the maintenance while mother was unemployed and step-mum was merrily ordering new carpet and then replacing it a month later.
Soooo my advice to step-mothers would be accept that you may be resented by small children (it's not their fault their parents split up, they didn't ask you into their lives) and don't force yourself into prominence at the family events of your step-children, or once you are divorced from their father!
Bet the MN step-mothers are a lot better-behaved than mine, though.