The AF on this lens is really pretty good. I also tried with a 1.4 TC v1 and although AF was as expected (not fast but still accurate and very useable) IQ was pretty bad. The light wasn't great though and IQ was on par with cropping at 600mm. I guess I should try it again in better lighting.
After reading all the Tamron reviews and user experiences and wondering if I should get one and worrying about AF I.m glad I waited and got this instead. I like the build since I'm not a fan of making a lens heavy just so it feels 'well built'. Strong and no sloppy movement, but obviously it is plastic and thus relatively light.
The only thing on the lens that feels a bit flimsy if the hood. But it fits on tight and I'd rather have to but a couple of extra hoods if I step on one or something than deal with extra weight just for the hood.
