Lumix GX1, Lumix X lens, blurriness

I must be lucky, as one of the first things I've done was to test my GX1 with the PZ 14-42mm lens at the far end of the zoom and at the problematic shutter speeds, both handheld and with a tripod, and I couldn't find any blurrines or double image results.

My camera is from January last year, and I'm using V1.1 Firmware both on camera and lens, OIS always on.

I also have the 20mm lens, and so far no problems, although I've taken only a few dozen shots with it since it is always on the GF1.