Tamron 28-75mm F/2.8 :thumbsup:
This lense is on my camera most of the time ever since I bought it 2 years ago. No regrets.
At that time, I was choosing between the Tamron, Sigma 24-70mm F/2.8 and the Canon 24-70 F/2.8L. The Canon was way above my budget, so it was dropped quickly. The Sigma has the advantage of a wider view, but slightly shorter telephoto, and it looks and feels and weighs more solid. However the large filter size(82mm!!) puts me off, compared to Tamron(67mm). Also the Tamron is smaller and lighter, easier to lug around.
Of course the final winning point is that I feel that the Tamron is sharper and gives better colour and contrast than the Sigma. Being slightly cheaper is a plus too(At the time when I bought it). Focusing speed is reasonably fast.
It is definitely much better than the kit lense and almost on par with the high end marquee lenses. Built and speed may not be on par with marquee lenses, but the Tamron is able to give you equivalent image quality for those with smaller wallet size.
Use the search function, these 2 lenses have been discussed many times before.