This. If I'm in the middle of something (watching a movie, web browsing, playing a game), I'd rather not have to switch to another app to reply and then switch back. I'd prefer to be able to just reply right then and there and carry on with my business. Yes, it is only a matter of a few seconds... But Apple's whole design is based on user-friendliness, intuitiveness, and sleek functionality. Having to exit one app to go into another and then switch back is none of the above.
I'm just hoping that BiteSMS won't take long to adapt to the new notification system if Apple doesn't include QR at some point in the beta process.