He seems to like it:

So is this M.Zuiko 40-150mm F2.8 Pro lens near perfect? It certainly is. I am scratching my head hard to find the flaws, which, honestly I dare say, is almost non-existent. The lens is incredibly sharp, capable of capturing amazing amount of fine detail, with almost no technical imperfections (well controlled Chromatic Aberration, distortion, etc). The bokeh quality is excellent, and handling with E-M1 (using HLD-7) is great. Focusing was extremely fast and accurate, with respectable close up shooting performance. You have all that in a pro lens, which is weather sealed against the elements, in much lesser size and weight than competition. Furthermore it is about 20-25% cheaper too.

Robin Wong is an Olympus Malaysia employee, so take these words with a grain of salt. That said, it’s hard to argue with some of the absolutely stunning images in this review: