Quote Originally Posted by neuroanatomist
Makes sense, Brendan. The physical build quality of the 17-55mm is very good (quite similar to myEF 100mm f/2.8<span style="color:red;"]LMacro IS USM, in fact), but what it lacks, IMO, is the weather-sealing of the 24-105mm.

That's halfway a deception in my opinion. Both are made of plastic, but the 100 macro is made of a higher grade "engineering plastic" and if I am right its build quality is superior (at least reviewers claim it's not built like an L lens, [:P] I dunno). The 17-55 also has a dust problem. Weather Sealing is huge to me, I am eager to finally get a combo (7d, 24-105, filter) that I can feel comfortable using in whatever conditions may arise.