How slow is slow? I would say it takes 0,5 seconds from touch to unlock and it works with the screen turned off. I can't say why it's not working with your phone. Double tap should also work if you have activated that feature.
I wouldn't say the camera quality is bad. You can't compare it with a twice as expensive phone. You can download GCam but it's only in some scenarios that it will do a better job. Our camera team is constantly improving the camera and our goal is to beat all similarly priced phones.