For me it's been exceptional since the 4.4.4 update and that's with some pretty heavy usage. Before it was only average. I hope lollipop doesn't change that.
I find it to be much better than the older EVO phones. During a typical work day my battery drops to about 68-72% and that's with moderate usage. On my drive home I slap it in my iBolt and it charges up about 15% so by the time I'm home I'm back up to 88-90%. I put mine on a charger every night when I go to bed and 100% when I get up.
Sidenote: I'm on Wifi most of the day as well. When I'm not on wifi the battery does drain quicker but not nearly as quickly as the previous phones had. I'm satisfied with it.
My wife just got the M8 for just over a week now. Similiar to Bassbiker. She unplugs at around 6:30am and by the time she gets home from work she is between 68-72% like clockwork. She is not on wifi all day as well, only data connection. She has all the radios on (Bluetooth, GPS, DATA, and Wifi). She has google now on as well as location services as well. Her on screen time during the day is about 2 hours. She easily can get a day and a half and 5 hours screen time. I am very envious of the battery life alone. I have the M7 and am trying hard to hold out for the M9. That 801 snap chip makes a huge difference. Her device stays 5-8 degrees cooler than mine during which is a big part of the battery savings.
To be honest battery isn't great for me after around three months of usage. I run the latest firmware and software and I get around 3 hours of screen time at maximum.
And how much screen of time you all get?
Go much? Dident understand youI keep brightness on 100% and get 2 1/2 - 3 1/2 hours screen on time... It also depends on how the lte is in my area...