The FA 100mm 3.5 Macro?

I am in need of a longer portrait lense, and I am waiting on a friend to try and source me a 77 limited in black, but I need one sooner. Since I have not got a macro lense, I am thinking about the Pentax FA 100 3.5 macro. Is this lense sharp wide open, and for close focusing? Has anyone used this lense for portraits on an *istD?

I don't want to spend alot of money on a macro, as I don't normally do alot of macros, and so the FA 100 2.8 is a little more then I want to spend at the moment, although Adorama does have the Sigma 105 EX 2.8 macro (older version) on sale. Whould this be a better choice then the pentax 3.5?

I considered the Pentax FA 135 2.8, but then I already have the sigma 70-200 2.8 EX APO, and the duplication in focal lenghth is not wanted right now (although I might get one latter on).

Thanks for your help.