Summary: I got this lens for such a great deal ($240)! Picture quality is superb (using on Panasonic G2). Lens is great for low light photography. My only concern is the lens emits a noise when focusing, this can be a problem when taking videos.
Summary: excellent lens, looks nice on a Pen. The view of 20mm is OK for most cases. Pictures are sharp and clear. But as discussed in a lot of forums, the focus of this thing is slower compared with 25mm f1.4.
Summary: I bought this lens for my new Olympus OM-D E-M5. It is my favourite lens: very small, very light, super fast and very sharp. :) Disadvantages of this lens (a relatively low speed AF and sound of AF motor) are immaterial for me.
Summary: I bought this lens for my Olympus OM-D, as all the reviews I've say this is the lens to own. I mostly use it for night photography and it works like a champ. The fast aperture makes for amazing bokeh and helps my OM-D sensor do it's best work at night. If I had anything negative to say about it, it would be the slow auto-focus, however I mostly shoot manual so I can't complain.