I have in my hands for a day or two a Panasonic Lumix GH2 and 14-140 lens to play with. I hope to give it a bit of a work out and let you know what I think of it.

This gallery is very much under construction and will take a day or two at least (likely longer) to be made complete.

Initial thoughts:

Camera:
There is an impressive number of easy to get at manual controls on the camera which reduces the need (thankfully) to menu dive. The menus are massive, but would become easy to use once the location of things gets memorized (like any menu system).
I don't think it would have hurt Panasonic to dedicate a button to focus point selection. I had to program the Fn button to that. Focus point selection operates via either the four-way controller (the camera is too cramped to reach this easilly when the eye is on the viewfinder) or via a touch screen (cannot use when the eye is on the viewfinder). This makes quickly changing focus points difficult although it does get easier with practice. I suspect that due to the number of steps needed to change focus points that it will never be truly fast. For one such as me who changes focus points between shots consistently and is used to a dedicated button for changing focus points and two control wheels, ease and speed for selecting af points is very much missed with this camera. On my E-3, I can switch the point by feel alone and have it ready before the camera reaches my eye.
Changing the size of the focus point is very very easy and I have found very good results to be had by using the smallest setting the camera has. The focus is very very fast, and very accurate in the test shots I have taken so far.
I really (really, as in oh for crying out loud really) wish that Olympus had sourced this sensor from Panasonic when they built the E-5. I would buy one in a second. I am loving it so far (low light test is coming).
The viewfinder is pretty good for an EVF. There is some tearing with panning and faster moving objects. My gut feeling is that this will only improve as the technology matures and refresh rates get upped. Nicely done Panasonic.
There is significant lag between pressing the shutter and a picture being taken (when compared to the E-3). This is not a bad thing, but it is worth noting. Significant means a fraction of a second, but it is enough that I have to adjust my timing to allow for moving cars entering a picture taken on a street where I don't as much with the E-3. I suspect that this is simply a case of adapting to it (let's face it, no matter what camera is used, this has to be allowed for - to me, it just stood out as being significant coming from my own camera).

Lens:
I wish it was brighter than f4 to 5.6. I understand why it isn't, I just wish that it was. The whole goal (or a major part of it) of m4/3 is to keep size down and if you make this lens an f2.8-3.5, the size would increase significantly. However, I think it would make the lens a lot more useful.
This thing focuses very quickly on the GH2 and is absolutely dead silent. I understand that this is very helpful with video (which I know nothing about) so I will have to play around with that before I return the camera.

Files: Something to say here already. The files from this camera are a delight to use. There is loads of resolution, and the raws are easy to manipulate in Lightroom 3. One thing I like is how easy it is to pull back blown highlights. There is a surprising amount of detail preserved in the blinky bits, and when they cannot be recovered, the gradation from blown to recovered is so smooth that it is hard to see the demarcation is.
This camera also makes it easy to generate decent quality black and white photographs with smooth transitions between the various shades of grey.