I've heard these rumors, but then there are rumors that the US government invented AIDS....
All I can say is, my new 3G S can last a couple of days, with tons of emails (push enabled), some internet browsing, some music, and a few other things. Oh, and I talk a bit.
And, here is what
Walt Mossberg has to say in the WSJ:
"Battery Life: On my 3G iPhone, I usually could make it through the day, but it was often a close call, with the battery indicator winding up in the red. By contrast, the new model did much better, never hitting the red zone and rarely requiring interim charging at the office or in the car, even though, because I was testing it, I was pounding it much harder than usual, making more voice calls, playing lots of videos and music, trying numerous apps, constantly downloading email from two accounts, and syncing two calendars over the air.
Apple claims about the same talk time for the new model as on the old, and about the same Web-surfing time over the cellular network. But it says the 3G S gets about 50% more battery life when playing videos or surfing the Internet over Wi-Fi and 25% more time -- an astounding 30 hours -- for continuous music playback."