4 stars because it doesn't fit tightly around the phone like other cases, for example the Ringke Fusion X, and that's kind of strange. I suppose this is because the case is flexible and slightly elastic, but still! If it cost half the price, okay, but paying over 50€ you expect it to be exceptional in every aspect.
I personally bought it because it's the only transparent case that has such good perimeter protection.
As for yellowing, only time will tell. I will update if it is...

Update after about half a year.
The case has yellowed completely and I threw it away because it wouldn't clean at all. I thought I wouldn't have such an issue at this price, but I was wrong.

I would not recommend it at all!