Initial testing was good, but some images appeared very soft when they shouldn't be. After digging through some forums and reading up a lot, I found this lens has a vibration issue that causes a "double image". Some people attributed it to the OIS (stabilization) but that is not the case.
I did some test photos with the shutter speed between 1/60th and 1/200th second. I know this isn't a safe shutter speed for the long end of the telephoto but you can tell the difference between motion blur and the double image problem. Taking 18 photos, at least 10 of them showed the double image. I took another 18 with OIS on and again 10 or so had the double image.
I'm pretty positive that there is something wrong with the stabilization lens, such that it sometimes vibrates even with OIS off. If I held the extended portion of the lens with my fingers, that seemed to decrease/eliminate the issue.
I could not recommend this lens to anyone until Panasonic fixes the issue and new reports come out of people using and testing it successfully.
I got my 14-42X as part of the GF3 kit. Possibly the newer versions have been fixed, but I haven't seen any evidence of that yet.
If you do buy the lens, please test it by going to shutter mode, setting the shutter speed to 1/60th, OIS off, and take 3 shots of a sign or something with high contrast (lettering is good) from about 10-15 ft away. Then up the shutter speed one notch and shoot 3 more. Keep doing that until you get to 1/200th. Repeat the same procedure with OIS on. Then review the pictures at 100% magnification. If you see the double image around letters, your lens has the problem.