If you want to record your screen in Linux, XVidCap is the best solution. It’s easy to install, able to capture fast without dropping frames, and offers lots of options.
XVidCap is really fast when capturing from the screen. I was able to capture Compiz Fusion effects at 15 frames per second, with no dropped frames or slow down. Other tools would drop frames when trying to do this. I took a video of Compiz Fusion, captured with XVidCap, to demonstrate just how well it works: