There is wide and then there is ultra wide
If you want to explore something more than pictures of people, food and the like, I have one bit of advise: get an ultra wide, learn to use it and you won't regret it.
I will never buy another camera that I can't shoot wider than 20 mm it is just that important. When APS came to market the big problem was wide, and honestly it took a while before we got lenses that were truly wide. At the time I collected the Sigma the Canon 10-22 was widely more expensive. Everyone was in favor of the Tokina in fact (as most still are), so I got the Tokina. But while I like things to be well made I don't love them to be made out of solid brass and break my neck. That is what sent the Tokina back to the shop, the Sigma had too things going for it at the time: 10mm and weight, and I could afford one.
All of my best pictures have been taken with this lens, and the HSM focusing system was the the first ultra sonic motor I ever had in a lens. The front element is surprisingly well sealed for standing next to waterfalls.
So what is wrong with it? Well in a word, the lens cap. It sucks, and it is harder to get on and off. I manage because I have tiny fingers but I can imagine others hating it. The front element is quite close to cap rear so you need to be careful if you want to change for a center squeeze cap, I have never been brave enough to make the swap.
The hood is excellent, the build is just right. Optically it might not be the absolute best ultra wide and I haven't had a chance to shoot with the Canon but I think this Sigma might still be the best value. But whatever your thoughts on this Sigma get something that goes wide, the wider the better.