So, this is made by samsung, for their flagship phone, and retails at £45 ish. I thought this was going to be a really good little case. I was kind of wrong.
Pros: The window is a bit of perspex, so you can happily put it in your pocket with your keys and they won't scratch the screen. The phone knows when the cover is closed and changes the display so when the phone rings the caller shows up in the window.
Cons: Replaces the back, so you can't have this and the wireless charging back at the same time. If you have the case open for a while (e.g. folded back on itself while playing a game) it takes a while before it will sit closed properly. It covers the movement sensor, meaning that my favourite feature (where you can wave your hand over it to light it up and show your missed calls etc) no longer works. It replaces the back with one which is slightly sturdier, but doesn't look anywhere near as nice and polished as the original did. It doesn't have the quality feel of the rest of the phone, the cover is a kind of synthetic fabric material. It isn't cut that neatly or finished that nicely. Cover doesn't stay closed (no magnets like in the apple equivalents) so if you dump it in your bag and expect the screen to stay protected then sometimes the cover may flap open.
Edit: removed another star as the area under the window is starting to get scratched. I think little bits of dirt get trapped between the plastic window and your screen, and then the cover moves around in your pocket, scratching the screen.