I've tried undervolting before (on my gnex) and it most often ended in my phone randomly rebooting and sometimes crashing overnight, the alarm not waking me the next morning. So I quit doing it...forever. I don't doubt that you might extend battery life, but at the cost of performance. I equate it to buying a porche, then having a governor put on it so it wont go faster than 45 mph to make your gas last longer. What fun would that be?
That's just how I see it, and I have to say that I have no major complaints about battery life. I use the phone the way I want, and if it gets near dead, I plug it in. Having said that, try it out for yourself. If you end up not liking having the phone undervolted, you can always change back to normal.