I guess I will be the lone voice of dissent here. Not only do I think they're ugly, I think they're inappropriate for something that I would consider to be sacred (as far as WDW goes). I would expect to see this on the local mass transit system, not at WDW.
I know Disney cross-promotes its products, but save that for something more innocuous. What's next, having a big Miley Cyrus poster hanging from the top spire of Cinderella Castle or a big Wand stating "Jonas Brothers" above SpaceShip Earth? What I mean is that I understand advertising is going to occur at WDW. ; There are some things I view as untouchable; the monorails are one such thing (and I know they've put those balloons and YOMD crap on them in the past...I didn't like that either, and that was to a much lesser extent).
As for Tron: Legacy itself, I'm betting there's fear that it will be a huge bust (which might have prompted this ad campaign). $300 million budget for a sequel to a twenty year old campy computer movie with only a cult following? I'm sure some executives are a little concerned about that...