The cool (warm) thing about them is there is no electricity needed. They are pricey and as Jackalope wrote, "I have one of the ecofans, and it works okay. It does move air, but the actual air velocity is pretty slow."
We have a ceiling fan which seems to work better in the winter. The first winter here we didn't have 120 volts and ran ours using a $99- inverter which was hooked to our battery/solar system.