If I was honest and looking at images at this size from different companies I don't think I could tell the difference. Could I tell that this image was from the GF1 and not from an Olympus OM-D? No I don't think so. Having said that there are a few lenses that do stand out and do prefer using them over others. This lens beats the Olympus 14-42 kit lens hands down in my opinion but I have read that others must have a steller Olympus kit lens as they find it very good.
This image was taken at an aperture of f/5.6 and at 45mm. So, it was wide open and it is actually quite sharp from corner to corner which says a lot for a kit lens.
The reason I actually took this image was because I saw a paddler going along quite nicely down the river Main. I'm not sure if I would do this as barge traffic is quite heavy here.