It's one heck of an expensive lens, if I remember correctly.
From what I've heard, the image quality is mostly pretty good, but there are some things that some people don't like about it. For example, I know a pro photographer who has used most Canon lenses and he didn't like the 16-35mm, specifically for it's flair characteristics. He prefers to use the EF-S 10-22mm. He has even modified it to fit on full frame or APS-H (1D) bodies...even though it does vignette.
But since you are looking to replace your kit lens, I'd suggest looking at the EF-S 17-55mm F2.8 IS. This one is a favorite of wedding photographers who use crop bodies. The image quality is on par with most L zoom lenses and it would fill out your kit a little more than the 16-35mm.
One thing to consider, is whether or not you think you will ever upgrade to a full frame body. I made this mistake and bought plenty of EF-S lenses (or similar from Tamron, Sigma) and then bought a 5DmkII. Now, most of my lenses won't work on my best camera (or they vignette terribly). So if that is a concern, the 16-35mm might be a better option.
Another option, that is upgrade proof, would be the 17-40mm F4 L. It's a high quality lens, like the 16-35mm, but I think it's less than half the price...and you only loose one stop of maximum aperture.