So long as they make sense and the unlock requirements aren't hideously tedious (i.e. beat the same game the same way 5 times. That's not fun.)
The other thing that amused me was how they said it was a first for a main-title Final Fantasy game. Even if you do include the -2 (and CC/DoC?) games as main-title for XIII-2 to count, it forgets that V had a variable ending.
First of all, they ALREADY made a game that didn't have multiple branching paths. It was called Final Fantasy XIII. And trust me, branching story paths have very little to do with the quality (or lack thereof) of the storytelling.
I like multiple endings and the freedom of choice it allows. See, because unless they make a sequel to this game (And oh god, please don't!) the "cannon" ending would be "whichever one I choose." After all, you don't have to view all them if you do not want to (and in the age of multiple game saves, you often times don't even have to replay the game all the way through to see all the endings)
I do not, however REQUIRE games to have multiple endings.
Multiple endings are generally a good thing, when they're handled well. It depends on how extensive the branches are before them. If they're only influenced by things at the very end of the game, then I find it feels like a cop out. If its a game that is focused on player decisions, and the decisions you make throughout the entire game determine the ending, then having multiple endings fits.
I think in a FF game the good/cannon end should be the only one available on your first playthrough though.