This is my story, I wanted to buy the GH4 since I own a GH3 but due to the fact it is not for available now I decided to give a try to the new sony ax100 which is also 4k. I bought the sony yesterday at bestbuy and I started to play with the camera shooting 4k video at 24fps. The quality is very good but I notice that even at slow movements or panning I see some kind of wobbling effect in the video. So the question is, does any of you have notice the same issue with the GH4?. If this some issue with shooting at 4k resolution or just with the ax100?. I asked because if that's the case I'm returning sony and I'll buy the gh4 instead. Thanks

If you're talking about RS (Rolling Shutter), it's there with faster pans (either camera). I'd suggest slow pans. If you plan to purchase the GH4, I'd suggest a good lens with image stabilization (like the Panasonic 12-35).

Rolling shutter is present in all these cameras. It's the degree that's different. I have seen a preliminary review on the Sony AX100 which mentions that it suffers from rolling shutter more than the GH4. Not a full review just a hands-on at a demo. My experience with the GH3 is that rolling shutter is minimal except in extreme circumstances. How that applies to the GH4, I can't say.

GH4's rolling shutter is basically the same as the GH3's.

I have a gh3 and it has RS but it's very minimum compare to what the xa100 generates in 4K.

The rolling shutter is worse in 4k on the gh4 compared to 1080p on either the gh4 or gh3 but not sure if it's equally bad as on the ax100, for that you need a owner that has both to compare. You can see more about the gh4 RS here (check starting from at 04:14:)
New Panasonic GH4 vs. GH3 Comparison [4K 1080, Moire, Rolling Shutter, Crop Factor, High ISO] - YouTube

Troy technically "owns" a GH4 but it isn't tracked to arrive until this coming week...

TIP O THE DAY:

If you turn peaking on with the GH4 the HDMI out goes interlaced and is no longer "clean"...

However, Troy (Me) has Technically tested the Rolling Shutter on the GH4 and Sony AX100 as my neighbor has both Cameras!!!!! My GH4 arrives on Tuesday (May 13th)............Thanks to Phil making that happen sooner than later!!!