I don't live in a 4G area... the battery life on wifi / 3g is great! I have my screen brightness turned UP because BEAUTIFUL SCREEN!
Since I'm diverting power to the main (deflector) screen
I have turned other options down: there is no reason to have the weather app updating every 30 minutes, my life is not so complicated that I have to ping for email every 12 seconds... that sort of thing.
As an extra benefit, I get to run Live Wallpapers (Blue Sky by Kittahface is bloody AMAZING looking)...
I get 15 hours of USAGE on stock battery and no root -- calls, emails, texts -- I predominately on wifi... days that are 3g only give me 11-ish hours.
These things work for me -- your mileage may vary.