Portable A/C Units

I was just shopping around for a window a/c for the summer. I never heard of this type of unit. Does anyone know how well they work? I checked them on line and they seem to be similar in price as regular a/c's.

I had experiences with two of them. Both from Home Depot, although the name slips my mind, they were around $300 each.

AND THEY WERE TERRIBLE. Don't use it in your bedroom, cause they're loud. Louder than a window unit. Also, it's not as effective in cooling, b/c the exhaust tube in the back radiates heat back into the room. You also have to watch out for the placement of the exhaust tube. Many models have the tube towards the bottom of the unit, thus, requiring you to snake the tube up towards the window. The tube is usually fairly large, in order to snake it up towards the window, you need a lot of clearance, usually about 2 feet off the wall. So your A/c will be sitting about 2 feet off the wall with a tube sticking out.