There are a good many lenses that seem to have bit of a problem when shot wide open, even many of the brand name lenses could exhibit a bit of softness at the edges, most lenses do have a sweet spot for optimum sharpness and I have even seen this in the high dollar Leica and Canon lenses, so it would be something you would have to test to make sure what the sweet spot of this lens would be, and that being said, if the price is low enough, I would go for it and have fun playing with it...

Dave