Summary: I love fisheye lenses; I own the 8mm Samyang fisheye for Canon EF-S mount and had great fun with it. This one is even better! Because it's so tiny, mounted on my Panasonic GX7, it's really easy to position it in interesting location.
Summary: I have the Rokinon version of this lens, another brand is Bower, all are actually made by Samyang. I also use it on a GX7 and I have to say I have a completely different experience than the one-star reviewer -- this lens is super-sharp and has become one of the favored lenses in my kit.
Excerpt: This is an exceptional lens. Don't let the price tag fool you. Some of my favorite shots have been taken with this lens. Just take your time during composition and mind your toes and knuckles.
Summary: It's a great lens with exceptional quality. I am not a professional so I can only comment on photo I took for personal trips, the side are severely distorted as one would expect from a fish eye lens, but I use it for landscape so the distortion is less visible.
Summary: Excellent mechanical stability. As others have mentioned, with F5.6 or higher manual focus is really a don't care as everything beyond a few feet is in focus. Works great on OLYMPUS PEN E-PL5. Nice bokeh. Only negative is that standard UV filters do not fit on this due to the built-in lens shade.
Excerpt: I have been using fisheye lenses for over 10 years, starting with a 16mm full-frame one for film Nikons. I have taken thousands of shots with a 10.5mm Nikon DX fisheye lens, and added this lens as my 3rd MFT lens. So far I have used it for landscapes and architectural shots.
Summary: I personally like this lens for a very wide field of view. Distorted, Yes, it's a fisheye. I use it on an Olympus OM-D E-M5, and really just have to play with some small adjustment. As a matter of fact, it will work on this camera when put on, with out a fuss.