I have a OM-1Markii and had the older 100-400mm lens. I was happy with it and when the M.Zuiko Digital ED 100-400mm F5.0-6.3 IS II came out, I did not think I would upgrade. After reading the reviews, I rented the new model and after two days decided to purchase the M.Zuiko Digital ED 100-400mm F5.0-6.3 IS II. The sync is amazing, the lens coating is great as less dust accumulated on it and the tripod collar which is removable is very nice

I had the previous 100-400 and sold it because it didn't seem sharp enough. I have the OM1 Mark II and I purchased the new 100-400. I am loving it. It is so sharp and you must have done something to the glass because the colors come out fantastic

I purchased this lens as a replacement for the Panasonic 100-400.The SyncIS of this lens is a huge upgrade. Sharpness seems at least as good as the Pany. I like the fact that the tripod mount is Arca-Swiss and easily removable. Zoom ring is firm, but smooth (better than the Pany). My only small niggle is the weight, about 5 oz more than the older Pany. But the IS is worth it. The hummingbird photo is at 400 mm, f/6.3, 1/2000 sec, and ISO 4000, on OM-1

I bought the OM System 100-400 IS II as an update from the Olympus 100-400 IS. It is a very good lens. Fast focus and tack sharp pictures. I have downloaded a picture of a Red-winged Blackbird to show its capabilities. Newer II is just a tad heavier than the previous lens.