Just curious if any EM1 owners have used the 14-150 on it? As my first lens, I'm getting the 14-150 as a walkabout lens, for longer walks around nyc. Specifically, I'd be most interested in your experience with this combination's autofocus speeds. I've also pre-ordered the 12-40 but am not excited about the weight, though i'm obviously excited about the constant f/2.8 and build quality. Thanks in advance for any comments on how the 14-150 is working out on the EM1.