Yes, I have the 8mm. It's a great landscape lens. You can pretty much eliminate the distortion by keeping the lens level. But the slightest movement up or down bends your horizon pretty drastically. In portrait orientation you get things very close in focus and things far away also tack sharp. But again, the lens needs to be level. The great thing about the Roki 8mm is that you set it to f8, set the focus just shy of infinity, and everything in your field of view is in focus.
"I know rocks. Rocks are hard."