+1 for Tamron USA service! I recently bought a couple Tamron lenses - 24-135 SP. It came highly recommended by everyone I talked to about it. I played with both for a while trying to decide which was the sharpest, which I would keep and sell the other. Sharpness difference between the two was negligible. The one I decided on had an incredible amount of dust inside and a little "hitch" in the zoom ring, so I sent it in to Tamron for general cleaning and calibration. They charge a flat fee of $150 for this lens. I sent it in less than three weeks ago and got it back yesterday. It is the same lens I sent in but it might as well be brand new. They replaced the entire aperture assembly, all the rubber on the outside, cleaned and calibrated. It is spotless and functions perfectly! And I didn't think it could get any sharper, but I believe it did. Can't beat that kind of turn around time either. Highly recommend them if you need something done on your Tamron equipment.