Lenstip posted the full Olympus 300mm PRO lens review:
The results are splendid in practically all categories apart from flares and in some of them (e.g. vignetting and chromatic aberration) they are simply sensational. Add to that one of the most efficient optical stabilization units we’ve ever had the pleasure of testing, a very good autofocus and a perfect cooperation with a tele-converter and it would be difficult to ask for more. I don’t doubt that the Olympus M.Zuiko Digital 300 mm f/4.0 ED IS PRO fully deserves the “Editor’s Choice” badge of LensTip.com.