Hi again bro, but won't you be missing the range from 55mm to 70mm? Also, I prefer medium telephoto for my general walkabout lens, which is why I'm set on the 15-85.
IMO, there is nothing much to lose between 55mm and 70mm. on the other hand, you have everything to die for even if it's just 1mm difference at the ultra-wide angle.
Don't you find 55mm rather limiting? That is the main reason why I prefer the 15-85 over the 17-55, although the 2.8 is dam attractive....
if i feel that 55mm is limiting me, i'll switch over to my 70-200L, so no worries about that.
granted the 70-200L is 1 stop slower than my 17-55, but the background compression still gives me decent bokeh and the IS mechanism is just amazing.