Although this post is about the Panasonic 45-150 f4-5.6, it's also about the G5 which is used in combination with the lens. I haven't used this camera a lot I must admit. Reasons being many, especially the new Fujifilm X100S and the X-E1. Both of those cameras are very good indeed but are not speed demons like the latest micro fourth thirds cameras now on the market.
The focusing speed of these new cameras is really impressive, especially the Olympus OM-D. The G5 is not far behind although it's difficult to appraise this because there's only a fraction of a second between cameras in this regard. I just have the impression that the OM-D is faster than the G5. The reason I purchased the 45-150 lens is because I wanted to take a two camera system with me when going out. The other camera is the GF1 (the original Panasonic m4/3 camera) which still takes great images. On the GF1 I mount the Panasonic 14-45 kit lens which is superb in my opinion. Using these two cameras gives me a 14 to 150 focal range without compromising all that range into one lens. Although I do use the Olympus 14-150 lens quite a bit, I believe these two lenses will give me better image quality overall.
For those interested, this image was converted using Nik SFX2. I actually took this image with a monochrome conversion in mind.