Our house is about 1200 sf, a bungalow with 2+ bedrooms and 1 bath. (The "plus" room is our home office/craft and giftwrap storage/music practice/catchall room, and it has the coat closet in it since there isn't one near our front door.) We've got attic storage space and a tiny detached garage-turned-workshop. (We park in the driveway.) The layout of the house is really very good, but it is just a little bit small for the four of us.
I want another bathroom, and as soon as DD is fully potty trained I'm going to REALLY want another bathroom!
: And I'd also like one additional bedroom, so that the kids can eventually each have their own room and so that they'd have a little more private/semiprivate play and study space. Because of the layout of our house and the small size of our lot, we'll have to add mostly up rather than back, so that means more square footage to account for a stairway, and we might end up adding a little more space to what is now the office to turn it into more of a "family room" just because that would make sense floorplan-wise. So I can see going up to around 1800 sf without feeling like the house was too big. And I am definitely not a fan of too-big houses with rooms that never get used!
Before we bought our house, DH and I lived in a townhouse style apartment that was probably around 900 to 1000 sf. Two bedrooms, 1 1/2 baths, with a large storage closet and a shared laundry room next door. It was a perfect size for just the two of us, although the downstairs did get pretty crowded when we had parties. The living room was kinda cramped for the amount of furniture and stuff we owned.
That apartment was built in the late '60s IIRC and when we moved into a late 1920s house it was interesting to me to notice the way the allocation of space has changed over time. Our house isn't THAT much bigger than the apartment and the number and type of rooms is very close to the same. But in the 1920s home, the bedrooms are small, the closets are tiny, and the living and dining rooms are relatively spacious. Whereas in the 1960s home, the bedrooms and closets are spacious and the "common area" rooms are cramped. I dunno, it says something about the meaning of "home" in our culture and the way our lives and expectations have changed.
Nowadays, of course, in newly built homes everything is gargantuan.
: I used to read a shelter mag that had a regular feature on "small houses" -- I believe they defined "small" as anything under 2000 sf. Some of the featured homes were little vacation cabins or quirky custom places, but there were lots of things that qualified as dream homes for me.
Those were usually right around 1800 sf.