Not tough at all.
I've had mine since July 12 and it already has a scratch right in the middle of the screen. I BABY my iPhone. My wife makes fun of me how I handle it. I keep it in my pocket with nothing else. I have no clue how it got there. A grain of sand maybe? I can't stress how much I baby it. I don't even set it down without resting it on the little black cloth my 3G came with. I am crazy careful. I am just sick over it. I understand I take some risk going naked, but this is ridiculous beyond explanation.
I love it in every other way though.