If it's accurate, it will be a good tool for diabetics. But most (if not all) diabetics should be monitoring their blood sugars daily or at least every other day and already have a pretty good idea how well controlled their blood sugars are. For a while, I was testing 5 times a day but now that I've gotten good control I've backed off to once a day alternating fastings with 2 hour post prandials.
I've always seen the A1C test as the doctor's way to verify whether or not the patient is reporting their blood sugars accurately and controlling their blood sugars consistently instead of just the few days before a doctor visit.
The A1C also can't and shouldn't replace daily self-testing. It gives you an average and doesn't show how high your highs or low your lows were.