Going from the 7520 Nextel to the Cingular 8700c, I am noticing good battery life. I have played with mine from 6am and it still shows full. I will know more at the end of the day but my 7520 would not be showing full with the amount of playing I have done.
I tell you I love the screen, for those who have not tried, check out the themes! Internet is FAST! No more WAP for me, 8700 is so much faster you can really do full HTML with ease with EDGE