Sorry to burst your bubble, but Ubuntu isn't really the best. I use to to use it alot before I tried other distros that suited me more, some of the ones I've used have better performance and lesser memory usage than what Ubuntu has.
If your computer has a dedicated video card inside then the drivers for that should be working alright, or if you only have Intel HD Graphics and it's running off that instead. If you have both then you might want to check about running both at the same time. The game could use some optimizations in it's performance I'll give it that, framerate may drop every now and then but it seems pretty stable in its current development.