So far, all we've noticed is a slightly flatter icon and some animations when toggling settings in the viewfinder. As usual, we'll poke around a bit more just to be safe.
Left: old, Right: new
The APK is signed by Google and upgrades your existing app. The cryptographic signature guarantees that the file is safe to install and was not tampered with in any way. Rather than wait for Google to push this download to your devices, which can take days, download and install it just like any other APK.
File name: com.google.android.GoogleCamera-2.4.022_(1549191-30)-24022130-minAPI19.apk.
Version: 2.4.022 (1549191-30) (24022130) (Android 4.4+).