My wife bought me one of these for my birthday (couple weeks ago). I got to use it for the first time on the weekend and thought it was really great. I tune really quite well by ear, but it takes me forever and I hate doing it. I found that I had all my lugs within 2 Hz of each other already (in most cases 1 Hz). That little bit of fine tuning I did with this made a HUGE difference. I think it is a great device.
That all said. I would think if you can't get it in the ball park of the right spot, it likely won't help you really improve the overall sound of your kit.