Also given your hands-on comment on it, I am considering this as my next lens. The 10-22 is also very attractive in so many ways (including its cost being half than the 16-35L), but I like the constant f/2.8 feature.
When we visited you in 2008, the 10-22mm was in the bag -- extremely useful for indoor snaps in Basilicas and the like.
My absolute favourite lens is the 16-35L -- that was my standard walkabout lens until the 17-85mm came on the scene -- now the 17-85 gets about 75% of the use for walkabout, and the 16-35L gets the other 25%. But we didn't carry the 16-35 to Italy last time.
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I missed it.
Cheers