I think the 17-40 is a good bang per buck lens, but it's getting old and the optical quality seems to be hit or miss with lots of copy variation. I'm waiting for the MK II, and if it's still constant f4 that's just fine with me. I almost never set my f4-5.6 lenses wider than 5.6 anyway because I just hate having the aperture change as I zoom. And besides, the long end is where you need wider aperture.
