I haven't really tested to Nexus 6 battery to the end as it always goes on charge with at least 30% left but a lot of people seem to be getting 5-8 screen time depending on usage. I don't believe it is as good on battery as the Note 4 when browsing the web though.
So far for the Nexus 6:
• Its currently unlocked, rooted & custom TWRP recovery installed
•Encryption removed to significantly improve read / write performance
•Updated to the latest 5.0.1 build of Lollipop
•Running a custom lean kernel which has improved performance in Antutu & Geekbench & also battery life
• Running -25mV undervolted across the CPU steps
•RGB colours tweaked as the Nexus seems a little warm & yellow out of the box.
Physically the size is perfect for me and it feels a premium device with the metal band. Also the stereo speakers are pretty damn good for listening to music / youtube videos, much better than a mono rear speaker.
Overall it is an extremely quick device, 6 months of play music was a nice bonus too (can finally minimise youtube videos & they continue to play!)
Can't think of anything else, but here is a quick snap of it idling nicely since doing a few tweaks. I just hope they bring out Xposed for Art soon *fingers crossed*