I carry a 60D and the canon 18-200 when hiking. It is not the greatest lens in the world.... but it is convenient. No swapping lenses in and out, easy to carry, and certainly decent enough quality for the web or slideshows. In hiking, what I can carry is the limiting factor.
As long as you are outdoors any comparable lens, like the sigma and the tamron, should act well. AF feed and image quality will be nowhere near as good as a nice Lglass prime.... but then again you will not be spending $8000 either.
Your worst case scenario is that you buy the lens at a great deal, try it for a while and decide you don't like it, and then sell it as almost new for close to what you paid for it..... not a whole lot of risk....