Interesting I use it all the time I find it fast and easy to use. Never really considered going into the Message app and opening. I'd use siri before going to the App Home screen.
My main problem with using the button as a way to quickly access contacts is that it's not very quick. You have to press the button, then rotate the crown (or just press someone on the wheel), then tap the "phone" "touch" or "text" icon and only then do you start actually contacting that person. I feel they could've done a lot more to streamline this.