WhatsApp beta app was updated to version 2.16.150 in Windows Store today. This updated app includes few user interface tweaks, with the app bar now hidden in the chat screen except when you are selecting or deleting items.
It also moves the call option to the chat screen and removes the Camera icon, meaning you have to go to the Attach screen to take a picture.
WhatsApp beta was previously a closed beta, but it appears anyone can now download the latest beta version (which thefore can come with issues) of the software.
Find it in the store here.