I can't believe some people are having these problems. It sounds like they occur mainly on older devices.
I'm running the Beta on an iPhone 5 and it runs slick as hell. No problems so far. In 24 hours I've had 0 issues and the battery life is just fine, same as it's always been.
There are one or two odd quirks, but they're not system breakers IMO. Occasionally Safari will hit a snag and stutter. It's also weird to have the old keyboard display inside apps that don't use the new one.
Besides that... I'm having no problems using this on my main device. If you have an iPhone 5 and the ability to use the Beta I don't see why you shouldn't. If you have an older device though, I might stay away judging by the number of bugs people seem to be having.
PS: I'm only talking about the core phone itself. Not third party apps. So far I've had no issues with Google Maps, Facebook, Google Earth, etc. but I have no idea what it will do to your games. Deep Dungeons of Doom seems to work fine but it's all I've tested.