To some consumers battery life is one of the most important features on a mobile device. Apple claims that the iPhone 6 and 6 Plus get up to 10 hours of internet use on LTE and up to 14 hours of talk time on 3G. If you are finding that your new iPhone is falling short of Apple's battery claims you may want to check the new battery usage tool found in iOS 8. Just navigate to Settings > General > Usage > Battery Usage and you'll find a list of apps and how much power they're each using.
The battery usage tool shows you the apps that have used the most battery life in the last 24 hours or last 5 days. The knee jerk reaction would be to eliminate these power sucking apps, but just because they're at the top of the list doesn't meant they're evil battery killers. It just most likely means you use them a lot.