The 1855 isn't just sharp, it's so darn good in every regard that I can't think of anything I would like to see changed except the size and mayyyybe a tad more bite at the long end. I still can't believe how flare resistant it is, it's almost immune and wipes the floor with any of my manual Zeiss lenses or other zooms in that regard. I like my copy so much that I finally cancelled my preorder for the 27.the 18-55 is quite sharp - sharper than what other kit lenses usually are. the main advantage of the 27, i think, is really its compactness. i have a pic on post 17 that was taken at f8 (i believe).