Okay, so I took the Tamron out for a spin this morning. I have had absolutely no time to do anything, so I haven't checked back/front focus on the lens yet. That being said, the event I shot was the Color Run. Lots of people, lots of fast movement. The kicker is that all 1200+ shots were taken at f2.8 only and AF-C. That meant many parts of each image were not in focus, and the areas that were within my center focus point had to be focused. I'm pleased for the most part, although the images are a tad soft, which really makes me want to test it out at all apertures soon (although I don't have time). There was plenty of room for user error, especially with so many moving objects within the frame at different distances. Move one hair in any direction with AF-C & I end up focusing on something else. As to AF, it is extremely fast. I'm not talking about going from near focus to infinity, but locking focus on a subject that is moving closer or farther away. In my usage, the AF easily felt as fast as the Nikon f4. Here are some samples (more on my flickr page):