Paul,
Agree pretty well across the board. As you mention, the 125 has a VERY fine focus 'screw pitch' vs the 100 ZF and from my experience almost any other lens I've tried including the Hassy 110/2 or Mamiya 200/2.8 APO (both fine focus pitch medium format glass I use/used on my 1Ds2).
As a Canon shooter (at least for now), the options via adapters are broader, so there are always a myriad of other lenses in a given FL to compare against (albeit with stop-down).
For me:
If a Canon shooter: Leica vs ZF vs CZ? Leica (used) every time.
If a Nikon user:
1. ZF vs. CV? ZF (better all-round lens).
2. ZF vs CZ vs 105/2.5 or 105 VR (+ some $$$ in my jeans)? Don't know, would have to try the Nikon's myself. My Nikon (D1, D1H) days were some time ago (although that may change with the D700).
I've had CA/PF issues with some ZF units such as the 35 and 100 WO or close to it in high contrast scenes and do wish for the price, the 100 had APO.
That said, I am tempted to try the 50/2 ZF M - reportedly very well corrected for CA (based on Lloyd Cramer's review) - would love to hear your thoughts on the lens.
Have seen some nice work from the older Nikon 105s and they seem to compare very well against the ZF for the $$$ (albeit on the one test I saw -
http://www.pbase.com/andrease/zeissais). On strong attribute of the 100 ZF vs. the competition is it's flare resistance.
An older test here did show a strong performance of the new 105 VR vs. the ZF on, I think, a D3.
Don't mind paying big $$$ for lenses (having gone through a Leica APO 'period' with the 90, both 180s and the 100), but to me a lens always has to deliver and handle in a manner commensurate with it's price tag.
Now, this is assuming I have other options to deliver what I want in that FL. If not, the lack of competition requires, in many cases, a premium, justified or not, be paid.
On Canon, custom encoded adapters will enable limited exif data, but it's not that big a deal not having it. As you mention with the newer Nikon bodies with AiS lens data input, EXIF is not that a deal. Much like yourself, I prefer lenses with an aperture ring.
On the construction of any new SLII line - probably right., but for the right price/performance in the mount I want, I'll put up with some flimsy construction ;>
A test of the 105/2.5 vs some other lenses folks might find interesting - can't vouch for the results as the 110/2 lens performance is far worse than I saw on my 1Ds2 using the 110/2 F.
http://24x36.org/tests/100mm/test100mm.html