Battery life is decent on the Rezound for a smart phone.
On everything stock, I was able to get 12 hours of moderate use out of it with 4G off, using only 3G or wifi. 4G is a huge drain. Listening to podcasts with the screen off should give you good battery life. The screen is also a huge drain too, considering it is pushing HD number of pixels. Battery life is even better if you uncheck the "Always Mobile Data On" option. Also, if you are on the go and manually turn on Mobile Data only when you need it, you can get very good battery life out of it.
What I like about this phone is that the battery life can be managed. How long it lasts will depend on how you use it. When your battery gets low, just turn off mobile data and lower the screen brightness, and that will get you through the rest of your day.
Rooted, I was able to get even better battery life. Almost on par with iphone 4. Currently, I recommend CleanROM 1.5 from Scottsroms. I've been getting very good standby times and decent screen on times with this rom. Battery only drops 1 or 2% per hour in standby.