This is one of the trade-offs. Last year when the iPhone wasn't 3g everyone was upset with Apple. Steve even came out publicly and said that the 3g chipsets weren't integrated enough or capable of handling power management more efficiently. A lot of people were upset, and said let them be the ones to dictate their own usage scenarios and manage it own their own.
Fast forward to this year, and I'm sure the iPhone 3g has a better 3g radio than whatever was available at the time for the previous iPhone; but now the argument is battery life is going to suck! You can't please all people all of the time.