Honestly, you might want to give Elementary OS a try. It's Ubuntu with a lightweight UI that feels like Mac OS X.
The newer version should be out soon, but Luna (current release) will have everything you need, be lighter on resources than plain Ubuntu, and feel somewhat familiar if you've ever used a Mac. Might be easier to get in to if you're worried about a learning curve.
But on the current Elementary version everything is outdated and the fact that the 14.04 based version is still not out doesn't fill me with confidence :/