I bought one of these Kenmore fans last summer and it works fine ever since out of the box.
Horrible- I bought three of these thinking they were the traditional two way fans that would help bring cold air in or push the hot air out- to start they are quite loud (if that bothers you)- but for all their noise they barely produce any wind. If you want to switch the direction of the air you have to flip the fan in the window- its a total waste of money.
They are easy to put in the window. The only thing I thought was deceptive was they say they are reversible which I thought meant you flipped a switch. What you have to do is take it out of the window and turn it around.