Advantages: (relatively) small and light, has a (manual) Zoom reflector 28-85 mm, and for more wide angle is a matt diffuser while.
Disadvantages: material and construction make a "cheap" impression, no display, pictures come a bit dark (correction +1 aperture), the reflector can be pivoted only in the vertical direction but not rotatable (which for me is the biggest drawback). Why the Olympus variant is locked as only a fiddly push button and do not have a classic knurled screw on the camera, is beyond me. I have the AF function can not be activated, but that seems to be a problem of the Pen E-P1.
Nevertheless, good value for money. Therefore, just as four stars.