Preferably a WebGL capable browser and video card, otherwise Three.js could potentially switch to HTML5 canvas.
On my MacBook Air runs smooth on both Chrome and Firefox. Same on Windows 8.1. Unfortunately, I can't test it on Ubuntu because I don't have a GUI installation of Ubuntu (I use the server version).
what does about://gpu say in Chrome? There are bugs in the latest version of Chrome for Ubuntu in both the Intel and nVidia drivers.