Just wanted to share my experience, since I wish I'd come across more reports like this when I was deciding what AC to buy for my New York City apartment.
I was looking for a couple of window units for two small rooms, both less than 150 square feet. I came across the small Windmill unit. 6,000 BTU's, looks less terrifying than many other AC's from an aesthetic perspective, and seemed to have a relatively invested brand behind it.
I bought two of them. One arrived broken, and Windmill replaced it. No problem. Before we even got to the peak of summer, it was clear, though, that they were having a really hard time cooling the small rooms. I reached out to Windmill and asked if this was normal. They suggested that perhaps one of the sounds I was hearing in the bedroom unit indicated a problem, so they replaced that one. But it didn't get any better.
Both rooms hardly ever got cool, not only during summer but even now. I'm writing this during the fall, and the unit in my office is on its coldest setting and can hardly get a chill going throughout the office, even with the door closed. I tolerated the one in my bedroom, but last year it started going on the fritz. The electrical system was shot, it would randomly cycle through different modes, change the temperature up to the highest setting and I couldn't turn it back down. I told Windmill, but since it was after the one-year window, they said they couldn't do anything about it. It wasn't their problem that the electricity thing rendered the unit unusable, even though nothing had happened to cause that. It was just their product degrading in a very short time.
That was disheartening because I'd hoped that these units would last more than a couple years without manufacturing defects making them useless. Anyway, I replaced my bedroom unit with a small Friedrich (which works extremely well in comparison). But just today, the same electricity problems are starting to happen on my office unit. Which means that both units I bought from Windmill, without anything on my end to cause it, have developed electricity issues that rendered them useless within a few years of purchase.
So in summary: the units are extremely, laughably weak, cannot cool at all. And, they apparently have terrible longevity. Waste of money.