If like myself you run a CyanogenMod based ROM (I'm using Mahdi) and want to try a new camera app then you can install a port of the OnePlus One Camera APK from XDA user elinho.

It has been confirmed as working on the following ROMs:

Mahdi rom

CM11

Nexus 5 Experience - CM11 Based (Andersonaragao rom)

Slimkat

AICP

I have only tried it briefly and it seems to work very well. I am not a heavy user of camera apps so I am not the best person to say if it is brilliant or not but it seems fine to me.

Download the APK from XDA.

Follow the XDA thread.