I received my OM System 45-150mm f4 today. I took a few test shots on my OM-5, and my initial impression is that it is pretty underwhelming at best. I was debating between getting either the OM System 45-150mm f4 or the Panasonic 35-100mm f2.8. I went with the OM System 45-150mm f4 after many folks on other forums recommended it over the Panasonic version.
I'm not a fan of the contrast, bokeh or color rendition. I'm probably going to keep it because I need this focal length for travel. However, I regret not going with the Panasonic version instead. Here's a sample shot taken with this lens on my OM-5:
