when my step-daughter moved in with us...my husband and i discussed how we would handle discipline and all of that jazz. it was decided that i would be completely in charge, just as if she were my flesh and blood.
and so i was. school, doctors, college, dates, dances, movies, talks...i did it all. i taught her all her life-skills...and have always treated her just the same as my blood-children.
when my husband and i split, hailey had just turned sixteen. she was placed in MY custody...where she lived until she was almost twenty. *crosses fingers* she might be coming home in january...
we didn't treat her a lick different...since i was already in charge of OUR girls...it made sense to just add her right on in. (probably helped that dh didn't WANT to be much involved). my family would have fell apart if we had different rule sets for each.
i guess my point is that there's a different dynamic for each and every family...and each and every one has to come up with a plan that's comfortable and right for them. there's no "one size fits all"...what worked for us might not for others, and vice versa.
Like everyone else is saying, I think it makes a huge difference if the mother is involved, and to what degree. It's wonderful that worked out for you and your family, but I think that is unique situation that you don't see very often.
In situations were both biolgoical parents are involved, I think that parenting role should be entirely up to the parents, not the step-parents. When the biological parents are absent and the step-parents are up to the role, more power to them, I think it's awesome-but when the parents are there, then the step-parents should know their place and step back.