I have had this camera for about a month now and shot 250+ images on two different lenses so I feel I can give some first impressions on this now. When reading this bear in mind that I've been a DSLR user for a few years now and was looking for a second camera that was very portable but lost as little as possible of the quality I have been used to in images. The camera I've been using for almost two years now is a Nikon D7000 and it is an exceptional camera. My comparison here is with this Nikon in a number of aspects and I realise that I am seeking very high quality images.
The actual body of the Gx1 seems mostly very well made and has a sturdy feel however it is not heavy. The exception to that is the cover over the three sockets (HDMI/Remote/AV) which is frankly a pathetic bit of plastic and I would imagine would not stand up to being opened and closed very well over time. The other slightly doubtful bit of construction is the rear dial wheel. As I will explain shortly this needs pressing in as a button as well as rotating and does feel as good as the rest of the camera.
I guess other than quality of image one of the main issues with any camera is how accurately it works out the exposure. I've used the camera mostly in A mode (aperture) or S (shutter speed). The exposure using "multi" or "centre" ("spot" is available) have tended to be no better than OK when compared with the Nikon (which is very good). However it is possible to have a live histogram on screen (and playback can be set to show highlight clipping) so adjusting the exposure is relatively easy once you've worked out how. The rear dial needs pushing in to take you into exposure compensation and then rotating, then pressing again to go back to altering the shutter speed or aperture. It did take me a while to do this easily but it works ok although I find I use it far more often on this camera than on the Nikon.
The quality of images from this camera has been very good. I shoot RAW and there is plenty of detail in the images. The lenses I've been using are the Panasonic H-H014E Lumix G Pancake Lens (14 mm, F2.5 Wide-Angle) and the Panasonic 14-45mm Lens - H-FS014045 (Micro Four Thirds Mount) (note this is either of the flavours of kit lens which do not get very good reviews). The images are probably not quite as good as the Nikon but considering the weight/size it would be very odd if that were not the case. The quality does deteriorate with increased ISOs and more than on the Nikon but is still good at 400 ISO though 800 is not really good enough for me (it continues to take passable pictures well above this is quality is not the main aim). I guess it is the fact that this is not as fast a camera as the Nikon that would one of the main issue for me.
Obvious good points * Weight/size make it a great camera to carry around. I do use the LVF which makes it a little bulkier however I felt I needed that because of the DSLR usage and it is very good (though not cheap) * RAW images and quality generally is very good with good size/quality options easily available * There is a "level" guide available onscreen which I like a lot (both horizontal and vertical) * The ability to store four custom user settings is great * You can assign function button (though two are touchscreen ones which I don't use as I use the LVF) * Setting generally are very good once you have been around them a few times. I like the fact that the "Intelligent Automatic" button can be changed to a press and hold to avoid switching to that accidentally. Equally the movie button can be disabled if that is not your thing for example.
Poor points * The fact that Panasonic decided to save 50p (?) a box by not providing a paper handbook is really irritating. A camera such as this which has plenty of settings needs a book you can read not a pdf that you open on your pc. Panasonic have also crippled the pdf so you cannot annotate it/bookmark it etc - very silly * While the handbook seems quite well written it certainly has some errors. The handbook states that in "creative mode" (black/white etc etc) RAW files are unaffected - not true, they are. This is silly as the whole point of RAW files is that they are unprocessed
I'll not comment on the touch screen as, using the LVF, I don't use the touch screen but it seems to get good press generally. Equally I didn't get this for movies though I have shot a couple and they seem fine. There are all the scene type modes you would expect on any camera as well as the creative ones and they are fine if you want that aspect of a camera.
I will add to this if anything crops up with usage however this is a very competent camera indeed for its size and weight. I didn't get this from Amazon - always worth looking around when buying higher priced items. It gives something fairly close to DSLR quality in a very small package. The lens you buy/use needs thought but I have no regrets at all about finally trying a micro four thirds and this will be with me more often than not.
* Added to after a couple of months use Having taken around 700 images now I do really like this camera. It has foibles but you learn to live with that. I tend to find myself catching the rear buttons when I get it out of the bag for example and having to "cancel" whatever it is I've accidentally hit. Equally exposure is a bit variable - mostly good but not as good as the D7000. I have found that single point autofocus on fast moving objects (specifically rally cars) leaves something to be desired but I still got some good shots.
As with most actual photographers video is not something I usually stray into however I have used it on this and for me (no expert) it was simple and high quality.
All in all a good, lightweight small but powerful camera.