I'm starting to think this thing is worthless. Based on a lengthy discussion on another forum, I gather that only the swing speed and angle of attack are accurate. It has no idea where the target is, so the numbers are instead based on the starting clubface direction and how close to square you have the device attached.
They claim it is internally accurate--it might not accurately state whether your clubface was open or closed at impact, but it will accurately tell you if it was more open or closed than the previous swing. I don't see how that is helpful.
I'm still hoping they prove me wrong, but at this point I'm not optimistic.