I finally got fed up with SourceTree and installed TortoiseHg on my Mac development machine. Read on:
This is a quick step-by-step tutorial on starting with Mercurial and BitBucket on Mac. This tutorial was done on Mac OS 10.8.2.
This is a step-by-step guide on installing Mercurial and TortoiseHg on Ubuntu, and setting up a BitBucket account. This was tested on Ubuntu 12.04 LTS and Ubuntu 12.10.