Panasonic GH4 review by Digitalrev.

The crazy guy named Kai reviewed the GH4 including also the shortest Still Image Quality test ever seen :)

Also Photofocus posted their GH4 review and writes:

The images are great. The interface is intuitive and quick and out of the way. The features are valuable, not bloating. The weight is half. The price is half. The cost of keeping heavy DSLRs will tell over time on your body and your hard drive. I think it’s really a winner

North American preorders, shipping date and price:
GH4 camera at Amazon, Adorama, BHphoto, Ritz Camera and Panasonic. Price: $1,698. In Canada at Vistek.
GH4 camera with interface unit at Adorama and BHphoto. Price: $3,298
Interface unit only at Amazon, Adorama, BHphoto and Panasonic. Price: $1,998

Europen preorders, shipping date and price:
Germany: Wexcameras, Marcotec-shop.de.
UK at Wexphotographic, CameraWorld, UKdigital, CVP, TipTop.
Holland at Fotohanskeuzekamp.
Belgium at Fotokonijnenberg.
Norway at Fotovideo.
Sweden at Cyberphoto, Skandinavianphoto.
Finland at Telefoto, Topshot, Verkkoauppa.
France at Photocineshop.
Spain: Fotoboom.

Asian preorders, shipping date and price:
Digitalrev and Digidirect Australia.

4K cards
Kingston 16-32-64 GB SDHC UHS-I Speed Class 3 at Amazon (Click here), Adorama (Click here) and BHphoto (Click here).
Sandisk 16-32-64 GB Extreme PRO SDXC UHS-II Memory Card at Amazon (Click here), Adorama (Click here) and BHphoto (Click here).
Transcend 64-128 GB High Speed 10 UHS-3 at Amazon (Click here) and BHphoto (Click here).
Panasonic 16-32-64 GB SDHC-UHS-I U3 Card (90MB/s) at Adorama (Click here) and BHphoto (Click here).