They do not slide around and keep their connection very well.
Number 1 absolutely need to add are track forward and backward buttons. When Paired with my apple watch, I need my Activity screen up and can't be switching to music to advance tracks. Second most needed feature, almost as important as first one is the ability to be paired to multiple devices. I shouldn't have to re-pair to a previously connected device. 3rd, and not so important would be wireless charging.