probably 40 minutes when using the phone to watch videos or something, my Motorola Q has HORRIBLE battery life if I'm watching a DIVX or playing SNES games. This is my .02 cents
if the iphone has 40 minutes of talk time (big if) by talk time they mean talking, which means the screen is probably blank as with all cell phones when you're talking. That means if you're using the phone where the screen is actually on, for like web surfing or watching video, you'll get much less then 40 minutes because big color screens drain batteries like nothing else. So what, you'd be looking at 15 minutes battery life? The Iphone may very well have poor battery life but I think this is a huge exaggeration. My Q when the screen is fully used I can probably get about an hour, if I'm just talking I get like 4.
I predict the Iphone will have about 2 hours battery life *shrug*