I just got a Komura 135mm f/2.8 with the finder and I love the fact that it's 1:1. Bright, good contrast with the framelines. I notice on the M bodies that the small offset from the vertical axis of the lens creates a significant parallax error up close. Not to worry, it's easily correctable but still a bit annoying. I'm used to wide angle finders so this is kind of new territory for me.
As for 135mm, I think it's a great focal length. With the long baselength of the ZI, you'd be able to focus the 135 more accurately than most Leicas except the M3. Might make a killer portrait combo.
Phil Forrest