Was there from 8am to midnight (I don't usually do this, but it was for a family function).
I knew I was going to be there all day and that battery life would be an issue. So I charged up 2 of the Chinese batteries I purchased on fleabay and stuck them in my wife's purse.
I unplugged at 6am to get ready and head out for the day. By 6:00pm, my phone was telling me to charge the battery. So I commenced to change batteries and went on my way.
At 1:00am, the cheapo chinese battery still had 60% battery life.
It really wasn't too much of a hassle to carry the extra batteries and there were people with "fruit" phones, a Droid X and a Droid Pro who were all having battery issues.
Mind you, I'm in a 4g city and I was pretty much twittering, facebooking and web browsing in every line.
I suggest anyone who is concerned about battery life try this. The batteries aren't expensive and worth not having to worry about running out of juice.