I've been thinking about this for a while, and I haven't made up my mind...I'm looking for arguments either way to help me sort things out. I'm not sure that the lens will really fill a need so much as a convenience. Here's my dilemma. I have a 7D, and the 24-105 is my main use lens. I typically don't shoot wider than 24 except for landscapes. There are times, however, when I'd like something wider, particularly indoors. I also have the Sigma 10-20 f/3.5. However, with it being 20 at the longest, I'm generally hesitant to switch to it for a shot or two, because not long after, I'll be switching back to the 24-105 again for more reach, and it generally seems impractical to be switching lenses just for a shot or two. It's also somewhat heavy to carry, and I prefer having a my Sigma 30 f/1.4 along with me for a fast lens as needed, and taking both won't fit in my preferred bag when I'm traveling light. In these kinds of settings, it's unlikely that I'll be shooting above 50mm, so 40 would seem to be close enough, practically speaking. My hesitation comes from the fact that I have the range covered already, and is the convenience factor worth the $1000 or so cost for the lens? I'd buy used, so it will likely be less expensive, but that's the ballpark. I realize that no one can tell me if the lens is worth the expense; that's a personal financial decision. But other pros and cons that I may not be considering would be valuable to me in making that determination. As far as other lenses that might fit the same need, there's the 17-55 f/2.8, which is only maybe $200 more, new. It would also give me a bit more range, and an extra stop of aperture. My hesitation there is weather sealing. Although I said above that my need is primarily for indoor use, I might use it outdoors on occasion, and prefer sealed L lenses. Plus, it's an EF-S lens, and since I also have an EOS 3, I'd prefer to have the lens I choose be compatible with that, as well. It's not a requirement, so I could be swayed, since realistically, the 24-105 could be used on the EOS 3 to cover the equivalent FOV at 17-40/55 mm. I'm not interested in the 16-35 due to the expense...that's definitely not in my range at this point. There's also the 15-85, which would probably be ideal, except that I don't like the variable aperture. Thoughts?