A., it's completely a personal decision. I decided to leave a very good job when I had my son, and I started consulting part-time from home. Then when I had my daughter, it was too much, so now I'm a full time SAHM. I personally love it. I think part of the reason I decided to do the stay at home thing, is because when I was in 8th grade my own mother was diagnosed with an illness and was given only a few months to live. It really has shaped my entire view of motherhood, and of family. Our time here is so brief, I really think the most important thing is our relationships. I want to be present in my kids lives. I don't want to miss a thing. I'd like to think my kids would rather eat macaroni every night with their mom around, then filet mignon and a mom they see briefly before bedtime.
But of course, you need to evaluate your own personal financial position and whether or not you can do it. It does take quite a bit of sacrifice. And I do plan on going back to work part time once my kids go to school.
Good luck with your decision. I know whatever you decide you will always have your family's best interest in mind -- and that's what makes a good mom a GREAT mom!