I bought the 18-135 STM as "Always plan" for my 550D. The lens is completely laulos. Unlike the USM you can hear the STM did not during focusing. Really amazing. The IS is also virtually silent. Only if you put your ear to the tube, you can hear him (of course only if you tap the shutter button). The zoom ring is very comfortable to turn. It wobbles nothing. The 18-135 STM is part of the new generation of Canon lens. Although it is made of plastic, but processed tired. It wobbles nothing. Really good! The picture quality is also very good. Surprisingly sharp at full aperture even in the corners! No front or back focus.
