Originally posted by pepperberry farm while I'm here - shots of the most recent arrival, the S-M-C Macro-Takumar 100mm f4:
You will love that lens. I did an extensive test between those two lenses and the older 100mm macro made for Pentax by a third party. You can't go wrong with either of those lenses.
The nice thing about the Tak is that if you are outside, the front element does not extend from the body or move inside the lens hood as it does with the DFA macro lens, not leaving it exposed to glare from incidental light or damage from twigs. That is a failing with the DFA. Look here:
Macro lens bake-off! - Page 2 - PentaxForums.com
Also, if you need to read reproduction ratios or distance, do manual focussing, or need manual aperture control, this is your lens.
Buy the dedicated Takumar lens hood (they run about $10) and it can be stored reversed by slipping it over the lens.