My fiancee's Dinc gets much better battery life than my OG Droid. She averages 20-30 hours (depending on usage, usually fairly heavy) per charge on her 1750 battery. I would gladly switch her but I don't want to stick her with my dying Droid.
I'd be willing to bet that HTC stepped up the battery life considerably for the Vigor, over the abysmal Blunderbolt. The dual cores, plus tech advances, and gb have probably helped tremendously.
I'm certain that either the Vigor or the Prime will be my next phone, just have to play the waiting game. A button-less Prime is mighty tempting though, since going forward devices getting ICS may look a bit silly with redundant capacitive buttons.
My guess is that it will most likely come with a larger stock battery as well. The stock Thunderbolt battery is 1390 mAh, the stock Bionic battery is 1785 mAh, the stock Charge battery is 1600 mAh, and the Revolution is 1500 mAh.