About the squared tabs:
Firefox 29 uses a background image to give the round shape. In order to let the colors show, I had to remove the background image. This gave me squared tabs that I really liked.
In the future version you'll have an option to control this setting and make the tabs rounded at the top like in previous versions of Firefox. (The bottom round corners are impossible to do; at least for now).
Currently colorfultabs detects whether it is being run inside Firefox 29 and then fixes the issues with australis. If the Firefox version is detected as 30, then colorfultabs doesn't fix the issues. Compatibility for Firefox versions 29 and greater will come in the next version.
Meanwhile, really overwhelmed to know that ColorfulTabs is such a widely used addon. Thanks everyone for using colorfultabs. More coming soon 🙂