I haven’t used it but from what it looks I would only use the Traits. I usually have already enough inheritance, so I don’t want to add another level of dependency.
Not sure what to think of the Setter Trait … I don’t see the benefit over declaring on-the-fly properties. When I need to use setters, I usually do it because of some value constraints (e.g. value must be an integer).
Something that would also fit into there would be an ArrayAccess Trait.