I agree about the part of fresh content and battery life.  I flew from Singapore to California on Singapore Airlines last Dec.  They had the built in IFE system with the Nintendo like joy stick.  They had about 30 different on demand movies of which about 15 were new movies that weren't out on DVD yet.  I also had my Sony Vaio TX which gets about 7 hours of battery life on the extended battery plus I had another battery so battery life wasn't much of a problem for me but most people's computers don't get more than a couple hours run time watching movies.  Watching a movie on an ipod is just ridiculous.  In the end I used the Sing Air IFE because of the content and accessibility.  I didn't have to have my computer on my tray or on my lap.  Plus the fact that the movies were on demand meant that I could take a nap then watch a movie without timing my sleep pattern with the plane's movie schedule.  In contrast I flew British Airways to Russia in Dec. and they had a similar built in IFE but wasn't on demand.  Plus their content wasn't very good.  I ended up using my computer instead of using their IFE.  Neither airline charged extra for the IFE however I would fly Singapore Airlines any day of the week over BA because of the entertainment value provided by their airline.