I understand your point Michael, there is quite some CA in the 100/2 Zeiss, however, the question here, I would have to answer as YES, GO FOR IT!
Why? I think the 105mm 1.8 is not perfectly corrected as well, and the 100 will outresolve the 105/4 by a lot. The price is really, really fair (in EU often > 500 EUR)
HOWEVER, I had the ZF 100 some months ago and compared it to my Voigtländer SL II 90mm 3.5 APO LANTHAR, which I commonly use as my "walkaround tele and sometimes close-up flowers etc".
While the ZF 100 is really good, my winner was the Voigtländer, simply because its WAY more compact, eases life a lot, as it was a lot easier to achieve focus.