I just read through this thread, and I think that is can all be summed up with "it really depends on your situation." For example, I can totally see working fewer hours, if possible, so that after-school care is not necessary, could lead to a net gain in income. Now for my long-winded 2 cents (feel free to ignore).
I'd have to agree with some pp's in being cautious about relying totally on child support. Though I am not divorced, I have too may friends who are and who get zero help from an ex to be comfortable with that arrangement. Besides the penchant for many men to turn into (expletive) after divorce, there is always the risk, in this economy, of job loss.
I do want to chime in and say that aside form child care, I think the monetary costs of working are often overstated. For example--clothing. I work in about as formal a setting as you can think. I wear suits, heels, and hose every day. However, those are are by and large intermittent costs. So when I began working, I spent about $1,500 on suits and shoes. Now I spend about $30 a month on panty hose and dry cleaning. I will probably spend an average of $300 per year of new suits and blouses. In almost any job that requires formal dress, the salary is going to justify the expense. In addition, I require far few casual clothes. I wear the same two things after work and on weekends over and over.
Another thing that is over-stated in the "tax" issue. Of course, as your salary increases, so does your marginal tax bracket. However, this only applies to the top percentages of your income. Therefore, if a person makes $10,000 or $100,000, that first $10,000 is still taxed at the same rate. The thing to be cautious about is reaching an income tax level that will make you ineligible for certain benefits, like earned income credit. In general, for 2008, a working parent of two can make up to about $39,000 per year. But even the amount of the credit varies according to wages earned. As you earn more and more, you will be eligible for fewer and fewer deductions. The big one for me is ineligibility for student loan interest deduction. However, I cannot think of a single incident in which a deduction would be more than wages earned.
I also want to pipe up with another reason to work. I know people may disagree, and that is fine. Everyone has their own experience, and I am not judging anyone's choices. However, personally, I feel so much better about myself if I am supporting myself. My mother stayed home with us, and we were poor. We always lived in crappy rentals, had to use food stamps and get free lunch at school. I never, ever got new clothes. I had to go deep into debt to fund college and grad school. My mother was always depressed. My parents fought about money all the time. Those wonderful homemade meals my mom had time to make because she stayed home consisted of the cheapest possible, unhealthy food. Believe me, there is not a day that goes by that I don't wish I could stay at home with my kids. I do not particularly love my job. OK, I hate it. But I know my kids are better off with me working.
As I said though, everyone's experience is different. It all depends on whether you are married, the age of your children, what jobs you are qualified to do, etc. etc..