I'd keep it an use it, I'd appreciate that someone has gone out of their way to find me something I'd like. Maybe your mother didn't quite get the right thing this time, but making someone happy is sometimes (always) better than having *just the right* camera.

Don't discard the box, maybe you see yourself as the kind of guy who buys old higher end gear un-boxed, but there is no need to pigeon-hole yourself like that, just enjoy the gift.