So there is a good chance you have arrived here in your search for that all-illusive "walk around" one lens fits all quest, like I did. If so, you need look no further.
I have used this lens now on my Canon 550D and then 60D for several years and have been very pleased with it. I have results like I simply could not have managed with the EF-S 18 - 55 kit lens, or for that matter my EF-S 55 - 250 lens.
Nice sharp pictures, decent low light performance and pretty fast, accurate auto focus.
The main gripe I have is as mentioned by others; the lens will creep if you point it downwards. I use mine with the Canon lens hood and this does not help matters. Rarely an issue but it is there, and for that reason it cannot be a 5 star in my mind.
Has not left my camera since I got it just about, it really does cover most of the bases, most of the time, and for this money it is a very worthy addition to your kit bag.
UPDATE: I have been using this lens for a few years now and have taken thousands of pictures on both the 550D and now a Canon 60D and it is still my most used lens. A real step up from the 55-250 kit lens and if you cannot afford or do not want to spend the extra for an L series lens this really is still a great lens. Aside from the lens creep it has proven itself to be a solid performer for me and has taken some very good pictures.