Strongly recommend this plugin. The formant pitch shifting is pretty much the only way I can get a good femme vocal recording from my testosterone laden cig-y vocal chords. The rest of the Soundtoys collection is pretty fantastic, but replacable. Alterboy is the only plugin I know of that lets you pitch shift the way it does.
PM'ing you
But just to say it, Bon Iver LOVED Soundtoys on 22, A Million. You hear a lot of Alterboy on the harmonies, especially the artifacting. You also hear Crystalizer a couple times too. Devil loc as well. Probably used Decapitator, people in his circle have talked about loving the plugin, Mike Dean being the biggest fan of Soundtoys in the pubic eye. I can hear it on the album very clearly, but have no proof. His mix engineer at that point was bigger on analogue equipment, so I could be wrong and he could just be using analogue equipment I haven't heard of. Devil Loc is modeled after the old Shure Level Loc, so it's entirely possible. But ST can still get many of those sounds