Hard to press lock button on 5s leather case

Keep pressing it until it is "broken in".

I would take it back if I were you, I never had that issue with any of the Apple leather cases I purchased.

Take the case off and use the eraser end of pencil to push the button part of the case out from the inside. Just a couple light pushes to break it in a bit. If you think it's that bad, definitely exchange it for a different case.

took a few days of steady use before mine broke in. much easier now than it was when I first got it (launch day).