I too once had a 17-40 f/4.0 for a while, then bought the 16-35 f/2.8 version II. I use the lens quite frequently, mostly for architectural work - both interiors and exteriors - as well as many outdoor environments, and any time I need the either the extreme wide angle to cover my subject at close quarters, or to achieve a desired exagerrated "perspective" look to my picture. I usually use it only from about 16 to 28mm, because my version is not very good at 35mm and I have other, better lenses at that focal length. The center resolution is wonderful for an extreme wide angle zoom, and I find the lens excellent, except in the far corners where the uneven plane of focus, gives somewhat unpredictable results.
I would rather have the new 17mm TSE lens if I could (and the new 24 to replace my older version) for my architecture, but my budget won't quite stretch that far for now; the 16-35 will do fine for now, plus, as a zoom, it is very convenient to use. The only thing I might add is that for architectural work, you should have a good understanding of post processing tools in Photoshop to help with the inevitable tilted perspoective issues that pop up with a non-shifting lens.