I am impressed with the 12-50mm but it is fairly big and it zooms in and out more like a camcorder. Just turn the ring slightly and it zooms with a motor. Your zoom time will only be as fast as the motor. No rush shooting.
There is a strange low noise sound from the camera. It sounds like a very small computer fan. I read it was ths IS working but the noise is still present with the IS off.
I had given up on Olympus until the E-M5. This one will do you a long time without an upgrade.