scotts33 good video and a cool looking device there. I think what he shows is a lot of what I had drilled in my head about my right palm has to stay up as long as possible and I shouldn't hear the swoosh of the club head until it is past the ball. All of that is hard to monitor, this little contraption kind of does that for you.
In general, you can pretty much tell your release pattern by the distance and trajectory you are getting if you are properly fit. If you tend to hit the ball high, and have issues with the pull or pull/slice, most likely an early release. Lower trajectory, later release. Distance is generated with speed, but you can max it with a good release, hence those stinger 2 irons we used to see rolling 300 yards by Tiger, high speed, should yield higher trajectories, but he didn't release that club, so it came in at putter lofts haha.