Its easy to turn on (or off) if you have a Jailbroken Device, I am on a 2G phone so I can't tell you if it works the same for 3G but I would think it would, here's what I did:
1) Upgraded to 3.0, and broke out of jail
2) Installed the latest sbsettings through Cydia.
3) Swiped from the top to pull down the sbsettings panel, and then tapped "More".
4) Tap Extras & Options
5) Swipe Numeric Battery to On and it should appear in real time with no respring needed.
6) Enjoy!
Hopefully this works for some of you, there is no way to do it without jailbreaking though.
As for taking it to an apple genius, simply restore to apples stock firmware and go see the Genius, or use sbsettings and turn the numeric battery off with that, they wont know the difference.
