Ours is about 2300sq ft main and upper plus another 800-1000 sq ft in the finished basement. It is just about right. We could make do with slightly less in the main areas as the basement makes a huge difference in how we use the main areas. The kids have virtually no toys in their rooms, just books and other than a couple of small bookcases and storage cubes in the family room all the rest of the kid stuff is out of sight in the basement. What I would like would be a 3 car garage because I don't know how we are going to fit five adult-sized bikes in the garage eventually.
Layout makes a huge difference in usability. Our last house had about the same main/upper area, but there was a lot of unusable space that made it feel smaller.
Mama to three boys ('03, '05, '07)