I have the SMC version. The Super-Multi-Coated was a real change from the non-SMC coated optics, what exactly that translates to in real reduced flare is questionable. I think even the non-SMC Takumars were pretty good.
I will say that the SMC Fish-Eye Tak 17/4 does produce some noticeable flare in some situations, but that it is better than my Tamron 14/2.8 and comparable to the Pentax-A 16/2.8. Just a couple quick examples - one of indoor lights that would wreak havoc with the Tamron 14 and one of the sun barely hidden that would probably be rendered satisfactorily with all of them.