I have an impression that I will be able to use it quite often. Take look at http://freehold.crocodile.org:8080/image_archive around October/November, you will see that the cooling is on only when the ambient is higher than indoors ('cause it drops really fast), however, I was really budget concerned and kept the house at 82F. Since the fan, especially the variable speed, is going to take a fraction of a cost, I wouldn't mind dropping the indoors to 75F, and the ambient sometimes drops below 68F in early September. The heating season, on the other hand, started on November 23 last year. Three monts in one half of the year is something to consider seriously.
Another thing, I see a need to further investigate the way the economizer is controlled - if it depends on "smart thermostat", then I've got it covered. Common sense tells me that this is probably the case. However, if I'm wrong and the economizer is a self-contained unit, I'll either don't install it at all, or install it and rip the guts out , or just put it together myself (well, good mechanics might pose a problem, but it's not entirely impossible). Dry bulb solution is going to cost me $3 per sensor, humidity is going to be more problematic because a) I didn't touch that part yet b) the sensors are pricey (last time I checked it was like $50) and they tend to be heavily backordered.
One more thing, the Trane manual I was looking at mentions that their economizer can work in two modes: if the air is sufficiently cool, it will just exhaust the indoor air and take the outside air in (I wonder how do they plan to filter it?), if it is not, but it's lower than the indoors, it's going to put the outside air through the indoor coil to just cool it further (filtering again?).
Usually an econo will do the job unless it's a computer room or something
This one I don't get. Computer room is way hotter than the rest of the house (4 to 8F is a norm), and will benefit from the colder outdoor air sooner than the rest of the house (actually, I was thinking about separating the A/C for the computer room from the house altogether, but it's noisy enough already). Can you please explain why do you think it's not going to help?
And to finish it on a light note, here's one:
"If you are over 30, you wake up in the morning and nothing hurts, you are probably dead".
I though it was a joke. Now I'm over 30