I wouldn't use a glass case for my iPhone. I know that it's going to look cool but it's not going to be a protective case for my iPhone. Imagine when the phone falls, and the phone case when damage more the phone.
I honestly never thought I would hear the words glass case and iPhone in the same sentence. Not sure that a glass case for any phone let alone the iPhone would be a good idea at all, especially not for me or my kids as we tend to be a little clumsy and have dropped our phones a few times and it has been the case that has saved the phone from damage. With a glass case, I can imagine not only the case but the phone as well would get damaged.