For video I have very little used, the STM works focusing on the 650D, but the feature I found in principle not so important. But can be quite handy when it is not the best solution for mitführenden focus is also in the competition there are probably more advanced systems.
For photography I found the focus really fast enough, though not comparable to some more expensive USM lens from Canon.
Aperture 2.8 is enough for most, even at night, for example, even in the light of street lamps and auto focus to capture sharp images.
Basically the focus is a little louder than USM lenses.
If you put more emphasis on light intensity and often want to take pictures in the dark, or even more intensive exemption of the photographed object from the background wants, you should probably grab the Canon 50mm 1.8 or to others of higher price ranges. The 50mm 1.8 I anyway slower in memory (and louder) have.
But with Aperture 2.8, you can create a nice blur in the background.
Only the operation of the manual focus is systemic (STM) is not optimal -The lens always requires power to focus and to re-retraction (others can be disable the autofocus simply enter via focus ring on, even if the camera is off). The lens is therefore not internally focused, such as an EF 85mm 1.8, which means it always moves when focusing a bit forward on / off.
All in all I am very satisfied with this lens.
