Unlike other phone-holding products available for your bike, RAM's offering is moulded specifically to the shape of the iPhone. As a result, it feels extremely secure - the phone clips into place and is held there from all sides, so there's no way it's going to jump free. Despite using zip-ties to attach the socket to the handlebars rather than a screwing mechanism, it manages to stay in place without sliding around, thanks to the adhesive rubber backing provided. Some damping of road vibration even takes place, thanks to the ball-and-socket style in which the mount itself attaches to its socket, while keeping the mount held securely - you have to rotate it to almost 90 degrees to remove it.
All in all, I'd recommend this, and I say this as someone who tried a competing product and didn't trust it!