We've got an iPhone 3gs at work for development purposes, spends most of its life plugged into a Mac except for when we need to demo something to a customer. 

The battery life is getting pretty average, like only holding charge for about an hour, has anyone had an iPhone battery replaced?  If so, how much did it cost and is it the sort of thing the Apply man can do for you right there and then or will we need to be without our dev phone for a few days?

Cheers