I think the 30-90 is fantastic. It gives me all the image quality I need, and it is super versatile. For me, the difference between 30 and 35 was also important because I found the 35 sometimes not wide enough.
I already posted is somewhere: A few months ago at the Leica shop in Brussels, I met the S2 product specialist for Belgium and France. He showed me prints made by a German professional who shot the zoom against the 30, 35, 70, and 120 in a studio set up (tripod and the whole shebang). At least for the center, it was impossible to detect a difference (if anything, the zoom had more micro contrast). These were full shot prints of a rear side of a Porsche 911 and 30x40 cm prints of half the number plate. Now, the primes may have the edge in the corner wide open. BUT: how much difference does that make in practice? When is you corner in the plane of focus when you shoot these lenses wide open? Not so often, I would guess. In any event, for me its a dawn good lens and I never regretted having put the money on the table.
Since buying it in spring, I have not used the 35 once. In fact, this year almost 75% of my shots with the S2 were made with the zoom (in 2012, about 25% of shots were made with the 35). I still sometimes use the 70 because it is so small and fast (and soooooo good). So I do not see any need for the 45 for me.
Now, if I only could get the 24
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Great weekend to you all.