It's interesting to see Trent and Maynard to start handing over more difficult vocals to other members of the band (or in some cases just change the notes to something more manageable). On one hand, it's a sad reminder that they're not the young bucks they once were, but on the other, it's preferable to them just retiring those songs. It's funny that songs like Branches/Bones and Shit Mirror are new - meaning Trent recorded the vocals within the past two years - and he's still not keen on singing parts of them live, but again, I'd rather he do it that way than not at all (especially Shit Mirror, which sounds pretty damn great with Robin).
That said, it'll be interesting if this opens the door to the band revisiting some songs they haven't played in a long time just because Trent isn't comfortable with the vocals anymore. We're In This Together and Last are two I remember him specifically making that comment about (and no doubt Happiness In Slavery lives in the same area).
P.S. I remember loving the Fragile tracks 1-4 opening in Vegas but thinking the whole time, "nah, there's no way they're doing the whole album; he can't sing We're In This Together anymore."