This lens was a nice surprise. I bought mine used like new (it is not produced anymore). I wanted a cheap option for UWA and I found this bargain. I was unsure about it because of some reports of its under performance in FF (I use a Canon 6D) but I cannot complain (too much) about it.
Cheap; lightweight; sharp enough (center); f/2.8.
Soft corners and vignetting wide open; some CA.