We probably belong to the unique group of users who aren't satisfied with even the stock firmware from Google, even though it gets the updates before other devices.
But a Stock ROM doesn't necessarily mean top notch performance. This is why we use custom ROMs, and one of the best ones for the Nexus 6 is the Pure Nexus ROM
Disclaimer: Androidpure is not responsible for any damage you incur. Try it at your own risk.
You will need an unlocked bootloader to proceed. Unlocking the bootloader will erase all data, so back up your data before unlocking the bootloader. It is recommended to take a full backup using TWRP Recovery, including your EFS partition, which has the IMEI information. Store this backup on your hard drive or on your PC. Also charge your battery to 50% or more before installing the ROM.
How to install Pure Nexus ROM on Nexus 6
1. Download the latest Pure Nexus ROM from the official website. (scroll down to the end of the list)
2. Also, download the GAPPS package. (BaNkS_Dynamic_GApps is a minimal one which we recommend)
3. Copy both files to the Nexus 6
4. Reboot to TWRP Recovery.
5. Tap on Wipe and select factory reset (wipe dalvik/art cache, system, data and cache). DO NOT wipe the internal storage, or your files will be deleted
6. Once it has been wiped, press the back button and select Install from the main menu.
7. Select the Pure Nexus ROM zip and swipe to flash it.
8. Wait for it to be installed, and once it is done, go back to the menu and install the Gapps package.
9. Reboot the device.
It will take a few minutes for the first boot to be completed.
The Pure Nexus ROM is pre-rooted, has USB Debugging pre-enabled, and has a plethora of new features. This includes Multi Window, Pure Nexus Settings (change lockscreen wallpaper, double tap to wake, status bar, screen recording, etc) and more. For a full list of the features, visit the XDA thread.
Also, the Pure Nexus ROM is constantly updated to include the latest security updates from Google. You will need to install a camera app, OpenCamera is an excellent free and open source alternative.
Benchmark fans will be pleased to know that the Nexus 6 scored an impressive 74870 points on AnTuTu.