Unreal should be a nice addition to the other games on Linux. :-) I tried the Ninja demo and it seemed fluid. Then I tried the Elemental Demo (we just watch right?) and it seemed to pause periodically through the demo. It seemed laggy in this regard and reminded me of when I play Rust even though that's a Unity game. It's still encouraging to see these companies get excited about Linux though, Linux rocks, no reason great game companies can't rock with it.