Camera ON/OFF button is more sunken in the camera body. It's now harder to turn the camera accidentally ON in your pocket. This often happened to GRD users, which lead to broken lens mechanism.
The power button now has a small green led light. Some people may dislike it, but generally, it's nicer to look than just green painted button. And one can always stick something over it
Settings1/Settings2 switch is now on the mode dial. It's great for fast switching between the custom settings (without the need to go to menu). Great improvement!
LCD is much brighter, with great viewing angles and much less "noise" artifacts if focusing (mainly in poorly lit room).
GRD2 is now a very silent camera! The GRD is loud at start and mainly during focusing, which is very disturbing and make the people to search for a source of noise.
Battery is now secured in the battery compartment by a small retention clip. I already dropped the battery from GRD because I forgot there is no such clip
Battery door now has a little spring, so you don't want to turn the camera down to be able to open the door.
There are two rubber anti-slippage "buttons" on the camera bottom plate. GRD has only one (GX100 none).
Significantly faster RAW writing. Yes, it still takes about 3.5 secs from pressing the shutter to complete write RAW + JPEG. However, thanks to a dual writing buffer, you can now take another RAW shot almost immediately after taking previous! There is only a little delay required (about 1sec) to be able to use the camera after previous RAW shot.
Because of the larger writing buffer, you can now take "unlimited" number of JPEG shots (limited only by a card size) with constant speed 2.3fps. With GRD you can take only 4 JPEG shots at 2.7fps and then the speed drops to 0.8fps.
The high ISO images appears to be cleaner in RAW. ISO800 from GRD2 is like ISO400 from GRD. And there does not appear to be any (visible) RAW NR applied.
Auto WB (and WB as such) is greatly improved in GRD2! I'm now using GRD2 almost all the time in Auto WB and it works flawlessly. GRD WB is not that precise and it's better to switch the GRD WB modes.
Flash accuracy and usability is improved too, although I'm not using the flash much The number of overexposed flash shots is significantly lower. And even thought the GRD now also has the option to manually adjust the Flash power, form time to time it just doesn't work or doesn't work well?
You can hold and review the picture on the screen right after taking it, zoom it or even delete it. This is a nice workflow improvement over the GRD.
Auto ISO can be limited to ISO 200, 400, 800 and 1600. I believe the max auto ISO in GRD is below 400?
Orientation sensor. Nice little addition which auto-rotates the pictures in preview mode but most importantly, set the correct orientation flag in the image Exif! Most of good image editors and viewers can auto-rotate the images to their correct orientation.
Electronic level. Some people say it's just a gimmick. I have to disagree with that. Sure, you can fix the image level in the image editor. But remember that any image rotation degrades the image quality and you will have to crop the image after rotation! I have the level permanently ON and it's very useful option!
GRD advantages over GRD2:
GRD does much lower NR in JPEG. This is very good and important for postprocessing. The lower NR level gave the GRD pics a very special look, for which is GRD sought by many artists. The GRD2 now applies strong NR even with NR set to OFF and in my humble opinion, it breaks the famous GRD look. The effect of NR is mainly visible in dark parts of the photo and large areas of the same color without much details.
If you use mainly JPEG, the GRD2 is probably not the best choice for you. I really hope there will be a firmware fix for this, which will allow us to turn the NR completely OFF.
Sound note to picture and Sound Recording mode is gone from GRD2. It would be rally interesting to know why? Both microphone and speaker is still there and you can still record sound with movies. So why not with pictures or just record the sound?
GRD2 cannot use full range of apertures/shutter speeds. f2.4 is for example limited to 1/800. In GRD you can set f2.4 to 1/2000.
GRD function buttons are matte, while GRD2 buttons are glossy. The matte buttons looks definitely nicer and more exclusive. The glossy GRD2 buttons looks like from a very cheap camera.
GRD Adj wheel is much faster to use than the GRD2 lever. It's especially visible in M mode, where the Adj lever is dedicated to shutter speed. And the lever definitely slows down the shutter speed setting.
Phase detection AF. It's another mystery why was the passive focus removed from GRD2 (probably a price cut?). It's a pity because it's visible faster under good lightning conditions. But it's important to say, that the GRD2 CCD based AF seems to be faster in poor lightning conditions! The GRD always starts with passive AF, and if there is not enough light, camera switches to CCD based AF (which is significantly slower in case of GRD).