I have now gotten a ZI with the 50mm f2 for myself and I can see the issues raised in the previous posts. Three years ago, I got the opportunity to travel to Paris a few times for a work related project. Because all my equipment was too bulky, I picked up a Contax G2 and a few lenses. A quick comparison shows:
*I liked the G2 for the auto-wind/rewind (not applicable to the ZI).
*It was faster and quieter than the user-group posts implied.
*The surface contours fit the right hand very well with a positive grip (much better than the ZI narrower body).
*I liked the zooming feature of the viewfinder, which I believe goes back to 1950s design (not applicable to the ZI).
*Best of all, it was incredibly cheap compared to other choices.
Now the negatives:
*The viewfinder is much too small and placed too far inboard for comfort, although it works OK in the vertical position (the G2 is like looking through a peephole; the ZI is like opening the door).
*No focus scales on the lenses (its not really a manual focus camera no matter what the manual states).
While I liked the G2 in operation, I found many shots were just too soft because of the auto focus not locking where I wanted. If you used a reasonable aperture, it could be a marvelous street camera with first-rate optics. However, I always had control of focus in my other equipment, so I never quite got over surrendering to the automation (auto exposure is much easier to adapt).
Final Decisions on a ZI Outfit:
I decided to go with the 21, 28, 35, 50, and 85 lenses. The range from 28 to 35 is small (12 degrees) but 35mm is the best all round strolling lens. I believe in lens hoods and this selection can be covered with only 3 hoods.
I dont think the full-frame approach will work for a 25mm lens. The edges of the full -frame view are too soft to use and to see them it is necessary to adjust the eye point quite a bit. Even a slight off axis look through the viewfinder makes the 28mm bright line hard to see. If it were a sharp outline while in normal viewing I could see using it. I would reconsider if someone was to measure and post the results; maybe the 25mm doesnt need to go to the edge of the frame but just a ballpark distance beyond the 28mm frame lines.
Without the 25mm, I decided to drop the 18mm because of: 1) the wider the lens, the less likely it is to be used, 2) it would require another set of filters, and 3) I couldnt work out a single external viewfinder option with the 18/25mm combination. The Leica 18mm viewfinder includes a 24mm equivalent view for 2/3 digital cameras but is $750.
So, that is where I am now. Over the next few months Ill place what isnt nailed down on the auction site and watch for these lenses.
Thanks to everyone for their responses.