Jim Chung reviewed the Yongnuo YN455 Micro Four Thirds Camera and concluded:

In addition to a terrible AF system, the camera fails to satisfy the standards of the m43 lens mount.  M43 manual focus lens like the Laowa 7mm f/2, 43rds lens using the MMF-1 adaptor and EOS lenses using a Metabones adaptor do not function at all on this body.   The error message displayed reads:  “The lens is not ready.  Please unscrew the lens to the proper position.”   Which is beyond cryptic.

And also in violation of the standards of the m43 lens mount, when a new lens is changed, the aperture does not default to the largest aperture of the new lens but maintains the last selected aperture.

It is hard to imagine the decisions that lead to spending millions of dollars to tool up and fabricate this camera when its market and audience is so unclear.  It’s not a camera for smartphone users because the thing is a brick.  It literally has the dimensions of a clay brick used in domestic residential construction with even a small to medium sized lens attached.    And it’s not for the serious photographer or dedicated m43 user because the poor AF system means that it cannot take full advantage of its interchangeable lens ability – the ability to use quality high focal length optics that will always be beyond the capabilities of smartphone based cameras.    Even the Yi M1 is a better camera.  A much better camera.   You can see my review from several years ago  https://jimchungblog.com/2017/02/03/a-real-world-performance-review-of-the-yi-m1-camera/

ePhotozine tested the OM 12-40mm lens and concluded:

There is little sign here that the smaller MFT format is causing much in the way of diffraction issues with this lens. Sharpness is maintained throughout the aperture range and also throughout the focal length range, to an extraordinary degree. There have been many claims in the past that zoom lenses perform as well as any primes within their range, and in this case that is definitely true.

The cost of this is a slightly higher price and an increase in bulk, but the latter point may be moot as the lens is not particularly heavy anyway. We really see the benefits of the compact nature of the MFT format here. It is just possible that some might choose the more compact 12-45mm f/4 option and save £300 in the process, but then again we have to set this against the more expensive lens that has a truly outstanding performance level.

It can definitely be Highly Recommended.