My wife just brought me a Tiffen UV haze filter for my Sigma, expensive but worth while. I realize that filters add a flare factor but I still like the security of having an extra glass to protect the front element (old habits die hard). I am getting some excellent results from this lens.
mtngal, I also haven't noticed any optical problesm like softness toward the edges, I guess I just don't look hard enough:-). I would also like a macro lens, the Pentax FA 100mm f3.5 is the same Cosina lens sold as a Phoenix or a Vivitar (except for the SMC coating), and these sometimes go for very low prices on ebay (or from the same source as this Sigma
). Apparently it is no great lens but quite acceptable to those of us who want to do some macro work but don't see it as our main passion.