I guess I should have said "IFE" instead of "seat-back IFE" since they're currently only ripping out non-seat-back IFE and only rumored to be ripping out the short/medium haul seat-back IFE in a couple years. I've edited my post.

My impression from observations is their seat-back system is a loser - no one wants to pay for live TV. The hardware is free to UA and they don't get a cut of the charges, but they have to haul around the hundreds of pounds of equipment on every flight.