I've had the 17-40 for a long time and recently bought the 24-105, Im finding the 24-105 locked onto my camera these days, my first lens with IS and Its great.
Im only holding onto the 17-40 as I plan on going full frame soon. (Ive decided that the range of this lens isnt that good on a crop body, 27-64mm? not great if you ask me)
However it is a stellar lens, length aside.