Hi Hillary,
Sounds like you have a great perspective already! We also have one daughter and life is good. Whenever the 'only' question comes up on here, I pull out my personal list of all the great things associated w/ having one child. Here you go!
Here are my views on our only child:
1. One child is less stressful! My patience is rarely stretched too thin (I'm NOT a very patient person by nature)
2. More funds on hand for outings/vacations -- we LOVE to travel
3. More one on one time with our child
4. No sibling rivalry or fighting
5. More time with my husband at night
6. Easier to focus on one child's homework at night
7. We only have a two bedroom house :)
8. Saving for college will be easier
9. My husband and I never have to "divide and conquer" as I see all of our friends having to do w/ their multiple kids
10. After nursing for 21 months, my boobs are still in pretty good shape. Doing it again? Forgetaboutit!!
11. I have the energy to play with our daughter!
12. Every little thing is special w/ our daughter :)
13. Family is very willing to watch one child while we have our adult time. Two or more? Don't think that would happen.
14. We honestly couldn't afford another child, whethere we were up for it or not
15. For us, one child is easier on our marriage
16. We're the 3 muskateers and a really close family
17. I never have to go through the intensive and sleep-deprivation infancy stage again!