I have been using Tamron lens and have particularly a very good experience, the prices too are very commutative and obviously the picture quality is on par with the original , the price difference between the genuine Canon and Nikkon lenses to Tamron lenses are huge as Tamron would always stand the...
Initial Cost is far less then the original Canon and Nikon lenses
The only negative point I see is the requirement of UV protection film on the lens for protection