What can I say? I've been waiting for a lens like this since I started into micro 4/3rds cameras about 5 years ago. The 12-35 f2.8 lenses were nice but I just opted for f1.7 primes because f2.8 really didn't cut it for me for quality indoor pictures. Especially in dim lighting. Well Panasonic finally stepped up to the plate and delivered a worthy useful Zoom lens for virtually any situation. Going from 10 Millimeters near ultrawide for landscapes/tight spaces to a very usable normal Zoom for shots of faces and even portraits with creamy backgrounds really is a dream for having that all in one lens. This lens with almost be a requirement for those that shoot weddings and want to use the m43rds format.The only reason this didn't happen earlier is because people have mistakenly held the belief that Micro 4/3rds is only useful being a tiny portable camera system and serves no purpose having large lenses. With the argument that you "Might as well get Full Frame if you're going to spend that much and use huge lenses". While that argument seems to make sense on the surface. I have an easy counter-argument: I don't want to have to re-learn an entirely different format, menu system and then have the extra expenses of new memory cards, new more expensive lenses, ND filters, and all the other expensive Full Frame accessories that come with it. On top of that there is very little benefit switching to Full Frame for me in terms of image quality. Dynamic Range may be the biggest benefit but the G9 has plenty of dynamic range for me and I don't want more than 20 Megapixel files. Shallow depth of field at f1.7 is equal to the quality of f3.4 on Full Frame and only half of a stop slower than Full Frame f2.8, which is still very good quality and shallow enough if you still want your subject to be in focus.Then why use Micro 4/3rds if it was originally designed to be a compact system you ask? Because you can use two camera bodies with any of the lenses in the system. I use the GX85 with the 20mm f1.7 because I can easily fit it in my cargo pants or shorts and bring it with me everywhere. I use the bigger G9 body with the 10-25mm f1.7 Zoom along with the 35-100mm f2.8 in a camera bag that has me covered for literally everything except wildlife photography, at near Full Frame quality. So anyways enough with the Rants... On to the actual Review:The 10-25mm is pretty much what I expected it would be before getting my hands on it. It's pretty huge but not obscenely huge like a Full Frame 70-200 f2.8 lens. Heavy at 1.5 Lbs but not as heavy as I originally thought it might be. I would probably not recommend this lens if you don't at least have a GH series body or G9 sized body. As it will likely be awkward with the 10-25 attached. Even with a G9 Body you can feel the weight as it is top heavy if you're only using one hand. I found that adding a Flash or External Microphone in the hot-shoe actually helped balance the weight. This is a lens that feels best when you have one hand on the lens and the other on the grip of the camera. This actually makes it very stable and helps with taking pictures at low shutter speeds.Speaking of shutter speeds, this lens has no Optical Stabilization. I do not find this as a problem as long as you have some of the newer Micro 4/3rds bodies as most of them already have great in-body stabilization and Dual IS doesn't significantly improve stabilization at wide angles in my opinion. However if you have a non-stabilized body I would probably not consider this lens. I have no problem taking photos under 1/10th of a second with the in-body stabilization of m43rds bodies though.Vignetting is noticeable between f1.7 and f2.8 but I didn't find it any worse than any other f1.7 prime in the micro 4/3rds lineup. Chromatic Aberration and Purple fringing are surprisingly low for a zoom lens with so many elements. Barely detectable and easily removed in photo editing software. Flaring is only really prominent when you are shooting directly into the Sun. If you are shooting at an angle close to the Sun I only noticed one colored blob that can again be removed fairly easily in programs like Lightroom. But I personally like a bit of lens flare myself. One of the few downsides of a wide aperture lens like this is when shooting landscapes in bright sunlight you can get diffraction resulting in some loss of detail at anything above f11. An ND Filter would help greatly for shooting in really bright sunny conditions.As far as audio is concerned, some people have complained about the auto-focus motor being noisy and being picked up on the internal Mics. However this is a problem with almost literally any camera. Even the mechanical noises of manually adjusting the focus ring will be easily heard when filming it quiet rooms. The only real solution is using an external microphone. Which is what you should be using anyway if you are serious about audio quality. When I used an external Mic mounted on the hotshoe, the focusing noise was almost completely silent. And of course using a Mic remotely or away from the camera will completely eliminate this issue.The manual clutch focus ring is indeed very convenient and so much easier than having to find the AF/MF switch on the camera body or digging through the menus to switch between automatic and manual. I have not thoroughly tested the Aperture ring for video yet. But it is pretty cool to be able to smoothly and silently change your Aperture manually for a more professional looking video. The Zoom ring is honestly the smoothest of any zoom lens I've used for micro 4/3rds. No stiffness or jittery transitions between focal lengths, unlike the 100-400mm Panasonic Zoom.Even the lens hood was ingenuously designed to not only be reversible to stay on the lens and fit in a camera bag but also locks into place with a tab that you can push to unlock it. Speaking of fitting in the camera bag... I had to reorganize by bag to fit this properly. I was barely able to fit it comfortably in my medium sized bag with the G9 attached. You want to make sure the lens is set to 13mm where it's at it's shortest length. I used velcro dividers that separate my longer focal length lenses on the bottom from the 10-25 beast that sits on top. Works out perfectly but there was not an inch of length to spare in my bag.There is really nothing other than nitpicky negative things to say about the 10-25 f1.7 lens. Obviously it's expensive. Many people speculated it would be even more expensive before it launched. But I can say after testing it pretty well for about a week, that it has met and even exceeded my expectations IF it holds up for at least another decade of use. I'm not someone that buys expensive things just to say I have it. I really plan to get my money out of it and use it as my main lens for 90% of photos and videos when I'm photographing special occasions. For casual use I've always got my GX85 and 20mm prime for portability. I've included photos comparing the two cameras and lenses for those curious. I'm sure this lens will be a legend talked about decades from now, even after micro four thirds was supposed to die out. 8-28: Couple of things I completely forgot to mention. The Autofocus is very quick and responsive. I only sometimes have issues focusing when using single point focus. I find the simple solution is to use pinpoint focus or make the focus point smaller. The never have issues.The close focusing distance sounds like a lot at 11 inches. But what most don't realize is that is measured from the sensor. Since the lens is 6 inches from the sensor when it's fully extended, you can focus within 4-5 inches of the lens. Which is actually quite impressive and close to macro abilities on this huge lens. Another testament to how useful this lens is.