Most of my TATL flights for the past 10 years have been on UA. I like the idea of IFE, but UA's movie selection so unsuits me that I almost always simply read the whole time or play with my Nintendo DS. I simply don't care to watch two month old blockbuster releases. I swear, it seemed like one year they were showing 'Mickey Blue Eyes' the entire year. On the occasions where I do want to watch, there is often much static flicker, or the movies in the guide don't match what is really showing. The IFE in the new C seats is obviously better though.
Now, the IFE offered by SAS, Emirates, and others is a different story. I like the interactive games, like the trivia game, or the golf game. I think I spent most of a NRT-CPH flight once playing the games. That golf game is really, really tough.