It's interesting to me the wide range of responses to this question...
I think we're finished at two. Though I don't like putting a definitive on that... because were another child to grace our presence, certainly we'd love him or her just as if we had planned in the same way as our first two.
Yet, DH has always only wanted two children, and three always seemed my "limit". Yet after our first, going from one to two was a HUGE decision, with TONS of discussion for us, and we didn't start trying until we both were COMPLETELY set on the idea of a second child. It really wasn't easy.
And my first pregnancy was emotionally difficult, labor & delivery was highly stressful, and took until the birth of my son to process & feel at peace with! My second pregnancy was in comparison, easy emotionally, yet difficult physically, and also came to a close in a highly stressful way, in spite of all our planning...
And on top of all of that, DH & I feel comfortable with one parent per child. We can give dedicated attention to each of our children, and honestly, I can't see myself dividing my attention during the day (as a SAHM) between three - it seems unfair - because I know myself, and my limits - and I feel I'm a good parent... and not sure I could be the way I want to parent with any more children.
So, likely we'll stop at two. Yet, DH hasn't made that appointment yet.