I travel a lot...but I usually fly either US Air or United (BTW - United is a much nicer airline...good thing they are in the Star Alliance with US Air so I get treated a bit better than normal members of the herd). However, recently I've flown a few other airlines. Quantas has awesome seatback entertainment (at least on their long haul 747's)...dozens of programs to watch including scads of movies and interesting TV shows...plus tons of good music. Necessary for 15 hours of flight time I can assure you.
Alaksa Airlines has an interesting concept, instead of providing airplane mounted entertainment they make you rent a "DigEplayer" for $10. It has movies, TV Shows, music, etc. Good concept (seems there are a lot of airlines that use them). Probably brings them a bit more revenue. The question is if it's enough to offset the cost of the equipment and the labor associated with it. They are very draconian in their headset policy though. I normally use my headset (Shure EC2s) as earplugs on take off and landing...I keep them unplugged from anything. BUT, on Alaska Airlines you can't have them in your ears...annoying. Oh well.
AirTran has XM Satellite Radio throughout the plane, kinda nice.