! I'm a working step-mom too. I know there are a few others around here as well - come on out, ladies!
I probably have it easier than some step-moms since my own child isn't around much - he's 23 and living on his own now. Also, my husband and I aren't planning to have children together, so we're just dealing with the ones we brought with us. My stepchildren are 13 (girl) and 8 (boy), and they're with their dad and me two nights per week and every other weekend. Their dad does most of the things that directly involve their caretaking, but we work together. My husband and stepson have a martial-arts class together on the weeknights that are "dad's", so I pick up my stepdaughter from her mom's and bring her to our house, but their dad gets them both to school in the mornings. My husband and I divide up the cooking and other household chores pretty well, and the kids are pretty well-adjusted (most of the time).
The fact that we have weeknights and weekends when the kids aren't with us actually helps
with the juggle, I think. I wrote an article
about that for WIM earlier this year. But if we had other children in the picture full-time in addition to my stepkids, I'm pretty sure it would be quite different.
I'd be interested in reading about other step-moms' experiences too.