I've owned and used the 7artisans, Olympus 1.8, and the Pansonic 3.5. They each have distinct pros and cons IMO. For the 7artisans, the pros are: low price, very nice build, compact, somewhat fast, easy to use, pretty good IQ. The three main cons: first, not very sharp. I had to stop it down pretty far to get only decent sharpness in the corners. For some applications, this wasn't really a big deal (i.e. night shots with no major action in the corners), but for others it was (i.e. a shot of a pool table and suchlike). Second, no autofocus. Third, does not take filters. For the Olympus, you get the fast 1.8 aperture, the build is fantastic, IQ is great, autofocus, and on some bodies you get the in-camera defish. Much sharper in the corners than the 7artisans. The cons: price, size (80mm) and weight (314g), does not take filters. Also, a touch slow focusing, especially in low light, compared to some other Oly lenses, but this might just be a copy issue. Finally, there is the rarely discussed Panasonic fisheye. Pros: very sharp (some online tests have it ahead of the Oly, I didn't pixel peep to check), very compact (52mm), super lightweight (165g), autofocus, and accepts filters (rear of lens). Cons: seems to have more purple fringing on Oly bodies, not very fast, some might not like the plastic build (although the focus ring is smooth). With respect to price, used copies can be found for 400-500, but YMMV. New it is only slightly less expensive than the Olympus. I can honestly recommend all of these lenses; however, given the age of the Panasonic, I'm not sure that the asking price for a new, non-gray copy can be justified. On the other hand, if you can find it used or gray, I find it to be a really unique and great lens.
