I have one on my iPhone 4, but it isn't a matte one. In my opinion, when you spend hundreds of euros on an iPhone, you want to take care of it. A screen protector is not going to ruin the user experience, a scratch on the screen will do it.
I used to be crazy about cases and screen protectors. Cases range from a few dollars up to $40-50! Add a quality screen protector.... it adds up!
I decided to purchase the AppleCare+ for $99 and then if I want/need a replacement is only $50 (up to 2 times though!).
I now use no case/screen protector and am covered in case of accidental damage or if physical wear and tear (which is extremely minimal for my release day white iPhone 5) gets too bad. I decided the money spent for a case/screen protector wasn't worth it. It also makes the phone bigger/bulkier, and heavier. I haven't had to use it yet.