GoldStar window AC - 600 sq ft
I have a GoldStar window air conditioner that I have used for almost three years. I live in an older, 600 sq ft apartment on the top floor of my building, and it can get quite hot during the summer.
The GoldStar has given me no problems in operation since I received it (I don't know how old it actually is, because it was provided to me by my landlord). It's a bit noisy, but not terribly loud.
I can't cool my entire apartment with it, unfortunately -- it isn't quite powerful enough. However, I can cool my bedroom with it very fast -- about fifteen minutes on high brings the temperature down to comfortable.
I generally run it all night, in order to be able to sleep. It has high and low options for both air conditioning and fan-only. It is a window unit that hangs out my window, which can be a bit awkward.
I take it out when it gets cold, because it does let drafts in quite easily, and it also blocks the light from the window. I'm not a big, strong person, so getting it in and out of the window usually involves a banged toe or two and lots of setting down to rest.
It is of course very electricity-hungry -- I can't run my hair dryer and air conditioner at the same time without flipping a breaker.
Also, due to its position relative to the roof, it gets splashed on when the gutter overflows. This can get very loud if it is raining heavily.