sony's 50 1.8 has much better build quality and looks than the Canon one IMO. and boy is the 100 f2 a rare piece of glass. its legend(wait for it)dary. just take a look at the sample pics taken with the lens. its definitely worth its price and those who have it are fortunate.
And we just had a Minolta 100mm f/2 on sale here in CS.
