Hmm, it's quite light, photos have sharpness on sides however all photos must be little sharpen (but I think it's normal). It works a bit loudly but I like this sound and not too fast (this lens is not for extreme situations when we need fast focus, it's need some work with that) and haven't macro function (I regret about that). Generally this lens is for architecture and landscapes photos and it's better than basic lenses of Canon or Nikon (like 'kit lenses' ).
You should try these lenses in practice. I want buy lens with macro function and big approximation and I'll choose Canon lens but better than 'kit'. And I read that Sigma lenses works better with Nikon that Tamron lenses but I'm not sure if it's true.