I had one (a Sanyo) that worked in that it blew cold air. But you should ask about two things:
1) many models have a water tank that needs to be emptied every 4-6 hours (depending on humidity levels), and mine sounded an alarm until I emptied it. That meant I couldn't sleep with it.
2) mine had a thick hose that went from the machine to outside, to exhaust the hot air. I had to buy a piece of plexiglass with a hole in it to put in my window. If not, and I just draped the hose out the open window, the hot air from outside would rush in to cancel out the cold air inside.