I should probably replace the ones I have, which are getting old. They put off a decent amount of cold air, but they're probably inefficient as heck.
I have the vents set up for my oil fired furnace (which I don't use, because it's hideously expensive), but I'm told it'd be "a bit" expensive to run the lines and install a central AC unit. I have two wall units for my house, and it's honestly good enough for all but the hottest days. I could fix even that by adding a third. The units are in the back of my house, so no one can see them.
Honestly, buying and tossing a $350 wall shaker every 5 years seems cheaper and just as efficient at cooling.