i have one. beautiful lens.
only small amount of fisheye distortion when pretty shallow into its focus... i wouldnt classify it as a dedicated fisheye, its really a wide angle through and through
i shoot mainly landscapes with lots of distance with it, its where it really excels:
probably gonna cut out the wires in this one:
from a recent mogul competition i was shooting at. im aware the reds are overblown, im probably gonna fix it when i have the time to shop all the pictures from that comp:
you can see the distortion in that last one though.