As other reviewers have mentioned, the installation is lacking. This fan could have EASILY been engineered to fit a far wider variety of windows. Lazy and shame on Vornado.
First, the instructions recommend keeping the screen on and ensuring the foam on the bottom of the unit seats securing in the bottom window casing. You can see in my picture that my window's design does not allow that. In order to keep the screen on (which I want to do), I must rest the bottom of the unit in front of the bottom casing. (Not to mention, if I had the space to seat the device in the bottom casing, the base of the foam blocks is too deep to fit in it well and too tall to prevent any gaps.) This is not a big deal, but it wouldn't have taken much change in design to accommodate windows like this.
Second, also in the pictures, you can see that the bottoms of the device itself as well as the foam pads doesn't extend fully to the sides of the device and foam pads. This leaves gaps of sunlight / air (if you didn't have a screen) between them. Why didn't Vornado just extend them fully to the sides? That would have closed up those gaps. <facepalm>
Third, the foam pads are WAY too stiff. I could barely squeeze in the last one to fill the final gap. I only had to compress it maybe an eighth of an inch, and that was ridiculously difficult for something like this. They could be made quite a bit softer and then be able to serve their function AND be easily installed (as well as allow for more differences in window widths as I cannot imagine if I had to compress the smallest one to half its original size, which could easily occur with an unfortunate alignment between window width and device / foam block widths).
I included pictures of the gaps at the top, as well. However, if I had been able to seat the device back in the casing as instructed, those would have been closed.
I only tested the fan briefly. All the modes worked. Its sound level was better than the twin blade style, though I do feel it moves less air. However, for my purposes, that is fine, as I wanted to switch to this style to block sunlight coming in in the mornings.
Overall, it seems like a decent fan, so long as your intention for it matches its abilities (as I mentioned - it doesn't put through as much air as the twin blade types). It's easy to operate. The features all work. It does "close" when not on (though there still is a little gap). It's just unfortunate such little tweaks that could have made it far more versatile were not implemented.
Worth $100? Probably not, unless you REALLY want a fan that doesn't let so much light in. If you want better air flow, save the money and get a twin blade. If you want the low profile for whatever reason, this still gets the job done.