The days of having '...but Nikon and Canon glass are...' discussions with yourself are long over.
I don't have a creatively styled image of the Fearsome Foursome just yet. It was hard enough trying to fit three f/2.8 lenses in the frame ranging 7-13 inches long.
This image from @tamronusa should suffice. (http://www.tamron-usa.com/product/lenses/a022.html)
Yes, it really is THAT good...in the right conditions.