It's really a preference thing. I have the opposite feeling, i.e. why keep OS X when you can run Arch? As for battery life, Linux can very greatly depending on

It's really a preference thing. I have the opposite feeling, i.e. why keep OS X when you can run Arch? As for battery life, Linux can very greatly depending on settings and distro. Don't expect to beat Mac OS without any configuration/tweaking, but if you go far enough you can get match it or do better.