Use this to film sports games, and it works really well. The insides of the bracket have foam padding inside, so you have to push down on the bracket with a little force before locking to keep your device snugly in place, but this was common sense to me. Others I guess not so much. This is not an issue while filming. This is only an issue if you are walking around with your tripod, and the device in the holder. If you don't lock it down tight, it may slide out.
The locking mechanism works well and stays locked in place. Have used it dozens of times so far, with no problems at all.
Only downside is that the plastic is a little on the flimsy side. This is not made from ABS, which is a much more heavy duty plastic. But, I think if you are just careful with it, it will last a long time. 4/5