7 out of 10 points and recommendedsmall, light, reasonable opticallysomewhat pricey, slight OIS issue at moderate shutter speeds
I had wanted this lens when it was announced, but given Panasonic's typical delays in supplying US stores, couldn't get one. In the meantime, lots of reports of severe OIS problems at shutter speeds around the 1/80-1/200 range near the long end of the zoom surfaced. Panasonic issued a firmware update which according to many people didn't help much if at all. Based on the direction of the blurring, it was clear that there was some sort of shutter-induced vibration issue which was probably a real hardware problem, not down to just firmware. I crossed the lens off my to-buy list.reviewed March 17th, 2012 (purchased for $400)
Time passed (still without US stock); I read a couple of reports of people who swore their copies were fine. Finally, Amazon got a few in stock, and after some agonizing I decided to try one and see if I got lucky.
The first slightly encouraging sign was that the lens came with firmware 1.1 already installed, so it was obviously of relatively recent manufacture. I had earlier tried a few shots with a copy of the 45-175X that did exhibit shutter-speeds-of-death OIS blurring, so I knew what to look for, and look for it I have in this lens. I can indeed see a slight hint of shutter-induced blur at 1/125 and 1/160 and 42mm, but haven't been able to find it at other shutter speeds. (I'm using a GH2 FWIW.) It's mild enough that I probably wouldn't have even noticed it without straining my eyes specifically trying to find it. At those two shutter speeds, it's further ameliorated if I rest my finger against the lens barrel while shooting. I would have to conclude that the issue is just not really field-relevant in the copy I received.
I can't really conclude anything about the distribution of bad vs good copies. It may be that most of the old ones were bad and the ones of recent manufacture are mostly good. Or it may be that it's just the luck of draw whenever it was made. All I can say for certain is that I have one that was made relatively recently and that behaves acceptably in this regard.
In terms of optical performance, I can only compare it to my current lenses. Here's what I've found from a day of shooting comparative tests.
At 14mm: my copy of the PZ, my 14-45mm, and my 14mm/2.5 are all roughly equivalent (generally good performance from all).
At 25mm: my copy of the PZ is excellent, notably better than my 14-45mm (especially on the left side), and about equal to my Leicasonic 25mm/1.4.
At 42mm: my PZ is acceptable, but definitely worse than my 14-45mm in corners (especially on the right side). In the center, the two are the same. Both zooms are put to shame by my Olympus 45mm/1.8.
Overall, I would call the optical quality acceptable and about as expected for a basic zoom.
Operationally, the zoom switch is a mixed bag. I somewhat prefer a ring, but I can live with the switch (the 45-175X, having both, was much nicer in that regard).
So what to say? It's obvious that lots of people have had bad copies of this lens. On the other hand, I have to conclude that the copy I got is basically OK. It fulfills it's basic mission of being a very light and compact zoom with reasonably competent optics, though not overall better or worse than my old 14-45mm. If you want one, I wouldn't do anything to discourage you, but I would caution you to buy from a retailer with a tolerable returns policy. Good luck!