Hugely important, like in iOS or Android..

Now wp7 only got 3 levels of brightness adjustment. We want a smooth linear adjustment like iOS and Android to customize our own brightness level.

pin settings like wifi, bluetooth, or battery percentage to start screen for live feedback of status

Give users the chance to set a timer for the battery saver function. So I can have it go on at night for example.

Allow creating custom power profiles
Ex: Home/Work (Wif on, 3g, bluetooth, GPS off)
Driving: (Bluetooth, 3G, GPS ON, WiFI off) Generic: (3G, GPS on)

Allow the phone to automatically turn on and off at user specified times, for example, overnight.

Allow the phone to stay switched off whilst charging and do not automatically switch it back on when it is plugged in to the charger. It's very annoying to have to have it switched on overnight whilst it's charging and it wastes power.

will very helful when there is low battery and also can choose which app to be live

Since Mango my Quantum can't even last half a day with nothing in the background. Make the OS more power efficient please!

A way for increasing your battery life for important appointement

To save battery, allow us to close tasks by displaying a little "x" in the upper right of each window.

It would be nice to be able to see the battery percent along the top without digging through the settings!

Allow the alarm clock to power on the phone. Leaving it on all night just for the alarm clock to work is silly.

Generally there is just the clock at the top Status bar. But if you swipe down that status bar, there could appear an additional Icon "Quick-Settings" (like in Android).
With Quick-Settings you could turn on and turn off for example power-consuming-sensors:
- Blutooth
- NFC
-Wifi
-GPS

I turn my phone off when I sleep. This extends battery life by about 30% (or 1 day for me). Create a scheduler for it.

I want it to turn off at 11pm and on at 7 am, for example.
It saves battery and saves me from unnecesary radiation.
All the phones I had for the last 8 years had that simple but useful option!

Phone turns off after 5 minutes when tethered or USB powered. Need to be able to disable that function

A power tile that can either activate the lock screen or turn off the display as if you were to push the power button.

At work I have a tv tower that blocks all cell signal and forces me to put my phone in Airplane mode while there or face a dead phone when I leave. Can't my phone do this automatically with geofencing? Also, can't you build a cloud database of all the dead zones per carrier and use this data, with some local validation, to work as a battery saving service?