It should improve your 'idle' standby times as long as you dont have too much stuff running in the background. Keep an eye on what you install and it could make a difference, maybe even a big one but this will differ from person to person depending on what they use the phone for and wots installed.

If you dont have much running when the phone is idle or no background apps run constantly then you should benefit and have spare power for when its needed.

when the phone is active, the big drains are 3g data wireless and screen but it would be nice to tune the device to idle along nice and slow saving mAh's for when you require it

When using the device though screen