I have one in my current home and also had one in my previous home.

Yes, they work! They just move enough air QUIETLY to keep a balance of warm air and cool air. If you're not moving the air, heat can build up in one room and the other rooms can be cooler than you want.

You place them on the upper part of a doorway or in our case the hall entrance right at the ceiling. Warm air rises and then is moved throughout the house.

We got one that sits in the upper corner. It was very loud and didn't move much air either. We now live in the south and most of our rooms have ceiling fans. They move a lot more air.

Good news!! Bought the doorway fan, installed it, and it has exceeded my expections. For a $25 investment, ya just cant beat it. Within 30 minutes, the second level temp rose 10 degrees F. And with a ceiling fan on the second level, it pushes the air up to the third level, and maintains a constant 68F. On colder days, I still need a boost from the boiler (central heat) to keep the entire house warm, however its obvious my heating bills are going to continue to go down. Yes, that fan is somewhat noisy, but we can live with that. Thanks again for your replies.