The ductwork in this house is frightening. There are new vents and old vents, and ducts going everywhere. The upstairs doesn't get enough air, and the basement gets too much. And there's no way to shut off then vents in the basement, so all of our air conditioning is going down there. Enough gets to the main floor to cool it off, but the upstairs is about 5 degrees warmer than the main floor. Doesn't sound like that much, but there's a big difference between 76° and 81° when you're trying to sleep.
I'm going to look into a way to re-work the ducts to make our heating and cooling more effiicient. In our old rental house, the furnace was located in the center of the basement, with a single duct going straight up through the house. All of the grates were located off of that duct, on opposite sides of the wall. If you were to take the grates off, you could see from one room into another. The neat thing about that arrangement was that in the summer, you could almost completely close the downstairs vents, and the cool air would all go upstairs (and since cool air sinks, it would still keep the downstairs cool). You'd then reverse it in the winter and keep the downstairs ducts open more so that the heat would naturally rise to the second floor. I'm sure there was probably a better arrangement, but that one worked extremely well for that house.
This house will be considerably more difficult, since it is larger and hasa less simple layout. First on my agenda is to find a way to block off the basement vents. One of them is a round ceiling vent like the kind seen in commercial buildings, and there's no way to turn it off. The other one is a wall vent, but it is unnecessary. In a smallish room like that, you really only need the one centrally located vent. I'm going to look for a way to disconnect the wall vent from the system. Once there's less A/C going to the basement, we should get more going upstairs. Just in time for cooler weather, of course. :)