Moving from my 17-40 f/4L to the 17-55 2.8 IS, I was slightly concerned about build quality, especially because I was buying it for PJ work. I had read a ton of comments here and elsewhere about how flimsy it felt, but I went ahead and made with switch.
Last Saturday, I was doing a shoot in a private cemetery on the edge of town. Waist-high grass and weeds, shed rattlesnake skins, and visible signs of their activity had me a little on edge. I was watching where I put my feet very carefully.
I was so focused on my foot placement that, when I circled around a tree to get a better angle on an old 1813 grave marker, I failed to notice the yellow jacket nest above me in the mesquite tree.
I got stung twice in the back of the head, once on each shoulder, and once on the wrist, by two or three of the suckers. In a moment of irrational thought, I just *knew* I was dead because a rattlesnake had just dropped out of the tree and bitten me.
In my flailing and wailing and cursing (I did apologize to the reporter I was with, but she said it was understandable!), my hat, my bag, and my 30D and 17-55 2.8 IS on it all fell to the ground, landing on top of a rocky grave site. Thankfully, the hood was on the lens. Oddly enough, my 40D and 70-200 2.8 IS stayed on my shoulder, thanks to the incredible UpStrap.
After the hornets flew off, I went and gathered my gear, fearing the worst for my "flimsy" little lens. Turns out, not a scratch on it, except for the hood, and it works flawlessly still. Turns out the non-L beauty can handle being flung to the ground in a panic!
So, buy with confidence that this thing won't fall apart in your hands, as some might try to tell you!