I noticed the unmistakable X Windows "X" cursor and gray loading screen on an in-flight entertainment system that crashed on me. I think it was Virgin America, one of their early flights after they launched.
But most new planes coming off the ground today are moving to Android based systems, since they have many advantages - it's much easier to get content like games and apps, and cheaper to engineer and develop for.
One of the problems with IFE systems today is that both A380 and 787 deliveries have been significantly delayed - often the IFE hardware is just sitting in a warehouse for several years waiting for the plane to catch up to it. So by the time the plane finally is delivered to the customer the IFE system may already be 4-5 years out of date.