As said many times in these forums: If I wait for the next great thing, I will always be waiting because next year the talk will be "Oh wait for the iPhone 6, it will be amazing!"
I went from a 4 to a 4S, and aside from Siri (which IS actually very helpful) you get to speak all your email, text, etc., the speed bump is awesome, and I truly do get better phone reception. For me, it was well worth the upgrade.
Also, I sold my old 4 and recovered the upgrade cost
As for the battery, I get more than a day of use, not quite as long as my 4 but close. (Usually go to the evening of day 2 and charge) Also, every year some people have issues. Not questioning if they have issues or not, but realize that mostly the ones who have issues will post. Those of us who do not have issues just enjoy our device. Mass manufacturing ANYTHING will have some issues pop up.... In my experience, Apple has always made it right for me.
Below is a screen shot of my current battery usage: