I'm not a "Pro" photographer but I have been obsessed with using and learning about cameras in the past few years. I have used the 35-100mm f2.8 lens consistently as it's been the most versatile lens in my bag for outdoor photography. Pleasingly sharp to my eyes. I'd recently gotten into taking action shots at my nieces games with the 35-100 and loved the results. I've found it very difficult to judge long zoom lenses because they have much shallower depth of field than shorter/wide angle lenses. DOF becomes very shallow once you go beyond 100mm and EXTREMELY shallow at 400mm. If your shooting a distant subject and cropping in a lot, then DOF is big enough to not be an issue. However cropping heavily will kill your image quality. Filling the frame with 400mm AND getting your subject in focus can be very challenging to the point of frustration.This is where I struggle to decide how much of my difficulties with getting really sharp/in focus photos with this lens is because of the very shallow depth of field or the lens itself not being sharp enough to justify the price tag. To be honest after extensive use I think it falls somewhere in between. I've shot some subjects from close range in pretty good outdoor lighting and had many shots slightly out-of-focus and kept the sharpest in focus pictures I could get. My best shots at 100mm seemed slightly sharper than the 400mm shots.. but again the Depth Of Field is also much shallower and more difficult to achieve good focus. The lens has Optical Stabilization built-in which is nice and also has a 5mm-Infiniti switch on the lens which helps with focusing faster on distant subjects. Overall I like the lens a lot and think it can take great sharp images with practice and experience. Even though there is not much to compare it to in the Micro 4/3rds long zoom arena.I have provided a bunch of previously RAW unedited photos converted straight to the highest quality JPEG I could of several animals that I took at a recent trip in Custer State Park, South Dakota to allow other viewers to be the judge. Most of the images were shot at pretty close range (around 10 feet away for 100mm shots and 20 feet for 400mm shots). The First is of a donkey at the shortest telephoto focal length of 100mm @F8 ISO400. The Second one is a Buffalo 400mm@F8 ISO400. A Third one is a Deer 350mm@F5.9 ISO800. The Fourth Photo is of a bird on a bridge that I shot at 400mm at only about 10 feet away. You can see how razor thin the DOF is at 400mm when you get near it's minimum focusing distance. In my opinion the shots are sharp but not razor sharp and I shot several photos with several attempts to get each of the subjects in focus in AFS(Automatic Focus Single) and CAF (Constant Auto Focus). I selected the sharpest of each of the photos that I attempted. Unfortunately all photos are heavily compressed and lower resolution after being posted on the internet. So keep that in mind.Pros:Very long and useful focal range of 100mm-400mmWeather sealed and nearly all-metal constructionAmazingly small and relatively light (2.1 Pounds) for such a range of zoomImages appear to be as sharp as my 35-100mm f2.8 at 100mm to around 300mmAuto-focus tracking seems to be pretty solid on still or slow moving subjectsCons:Zoom range from around 300mm to 400mm is pretty stiff and jerkyDue to the physics of long focal lengths getting sharp in focus images can be difficult at close rangeNailing focus on fast moving subjects is difficult with a low hit rate in my experience (May be due to camera/sensor more then the lens itself)Images at long end of the focal range don't seem to be tack sharp (could be due to focal length and missed focus)