Quote Originally Posted by Colin500

Do you (or does anybody else) manage to successfully use the f/1.8 primes wide-open for non-staged shots of relatively fast-moving subjects like small children?
Yes, but it's very difficult. There are several things you can do to make it easier. Try to tune autofocus into the best performance. Get a different viewfinder screen (they show thinner DOF). Try live view. Prefocus on a certain spot and snap it as the subject moves into it. Only attempt wider compositions such as environmental portraits instead of closeups. Arrange yourself so the DOF is parallel to the movement of the subject. Focus bracketing: rapid fire a lot of shots at slightly different focus or subject position. I'm sure there's more tips and tricks.