I thought I saw an article on DxOMark with a comparison and they recommended the Tamron, but that they were both better than the kit lens that Canon provides. I am waiting with baited breath for my Tamron - ordered last week.
I found Simply Electronics to have pretty good pricing on the Tamron.
Now that I have a few hundred shots with this lens, I am really happy with it. I took it into an old growth forest in dark shade, and took shots I know would have been more difficult with my Canon kit lens (18-55mm) handheld. The images are clear and clean - when I got the focus point correct... I'm still learning.
I have a birthday party to cover this weekend, and will have more.