Used the SMS Check in a couple of times (Monday and Thursday) myself this week on the QF409 service SYD-MEL. I for one would sign up to using this facility on a regular basis.
It works smoothly and does make life simpler for both passenger/s and check-in staff. One issue that takes away from this simplicity is when the aircraft is being refuelled while boarding is underway. I was handed a standard boarding pass and asked to turn off my mobile before boarding. This significantly reduces the value of the SMS Check in service.