40-150mm f/4.0 at BHphoto, Adorama, Amazon. GetOlympus. Calumet DE. Wex UK.

Photogrpaphyblog concludes:

Overall, it might not have all the bells and whistles offered by the faster f/2.8 lens, but there’s a lot to like about this new f/4 variant. It comes highly recommended to anyone who wants a versatile telephoto zoom that won’t break either your back or your bank account.

PCmag concludes:

The OM System M.Zuiko Digital ED 40-150mm F4.0 Pro lens covers the tight angles you want for telephoto imaging, and its tough, lightweight build makes it ideal for the outdoors.

OM Digital released the first part of their OM-1 development story. The Japanese text can be read here at Fotopus (and here the Google translation). Here is the text explaining the image you see on top:

This is a photograph just after the dustproof test. It is a test to prove that there is no intrusion into the camera even if you continue to use powder, which is like baby powder, for 8 hours. Of course, in addition to these, a powerful dust reduction system that allows you to change lenses safely even in the sand and a highly durable shutter unit are equipped with the same or better than before.

It is not only reliable because it is designed to prevent water droplets and dust from entering from the outside, but it is also developed with particular attention to making it hard to break by using even the internal parts, so you can use it with confidence.

OM-1 at BHphoto, Adorama, Amazon. GetOlympus.
OM-1 in EU at Calumet DE. Fotokoch DE. Wex UK. Olympus DE, Olympus UK, Olympus FR, Olympus IT, Olympus ES. Olympus NL. Olympus BE. Olympus AT. Olympus CH.