Does the IPhone 4 get better battery life in practical use than the 3G and previous models? how has your experience been with it in general?

After about 2 years of use the limitations of my Iphone are getting to me. Poor reception with ATT service (which I switched to for the Iphone like many) and also poor battery life. Ive noticed I use my Iphone functions less and less- I’m thinking maybe I want a different phone even though I’m very much in the mac walled garden of devices. Does the Iphone 4 have better practical battery life than the Iphone 3G?( I’m assuming it’s call quality is pretty much the same considering it’s still ATT. )If not what would be the best smartphone for battery life and functionality? any advice appreciated