I took out my new Tamron 1.4 TC (thanks honey) yesterday. It worked quite well. It does not report it's presence so the auto focus works just fine although it does hunt a little in low contrast situations. On these particular photos it had a tough time because I was shooting through a hole in the branches of a pine tree.
This is straight out of the camera. It is a photo of a fire lookout station on top of Buck Rock overlooking the Kings Canyon. I have been in the lookout and it is not a journey for the faint of heart. It is several miles away from where I shot the pic.
This is a 1:1 crop. I straightened it and gave it one sharpening pass in Picasa2.



