I agree that "thickness" is better word for it - I will change it in the next version. Regarding the default, everybody have preferences, I can bump it to 2px but would not prefer 10px (100%) - I want the progress bar not to be distraction - it's there if you look for it but you don't notice it if everything works fine.

Edit: v0.7 implements both suggestions, default thickness of 2px and labeled as "thickness" not width