I have a flip style case for my previous HTC Desire and that was good really but somewhat annoying that the case had to be open to charge, this more 'book-like' opening avoids that and if you want to keep a couple of banknotes or a card in there they aren't going upside down (fall out?) when you open it.
It's plastic PU imitation leather, seems reasonably sturdy but it is not as good as the real leather of my Desire one.
When clipping the phone in, put the buttons side in first.
Once in it feels secure however the clip/holder is only glued to the case and if you take it in and out a lot it will probably come away.
You can operate the three buttons with very little additional care, although volume up/down is not so easy as without it.
I found the stylus rather pointless and does not always work first time.
You can't clip it on the fold of the case as it does not then close properly.
I dislike screen covers, and there seems no need with gorilla glass unless you are very messy.
Openings for camera etc. line up well and sound from the phone is not much reduced.
It's useful protection especially from other objects in your pocket, it would probably save the phone from damage if dropped from around table height. It also makes it feel safer in your hand.