I to am not going again for #4 but if we did there wouldnt be a problem. I actually think #3 balances out the family more and for us she has completed us. She truly is a gift and i love everyday with my kids.
I know before we decided to have #3 Dh wasnt keen to spoil what we had and couldnt decide either way. He couldnt bring himself to say 'no more kids' though which was a positive for me. I just gave him time to think it through and get used to the idea of going again. I know he doenst regret at all of going again because she is so good natured and content.
Lukesmum, having #3 is far from HARD but the complete opposite. It is what you make of it to. I truly believe its the attitude of the parents that make the child. Im fairly layed back and not much bothers me so my kids tend not to stress either because mum isnt kwim. Just have fun with them cause they grow up so quick.
Jemima, you go girl! bring on #4. Time for a bigger car hey Lol. Good luck with the birth. I found that to got easier not to mention quicker.