I'd heard about this video from a friend some time ago but hadn't got around to watching it. This morning I did, and I'm very glad... Take a look, it's a 25-minute video of Bon Iver performing, basically stripped back to just piano and vocals.
The songs themselves, taken from the last album and the Blood Bank EP together with a cover of Bonnie Raitts' 'I Can't Make You Love Me', are a step back from their originals - the video description describing them as 'abstracted'. To me they sound as though they have been consumed through a lens that puts some more space into them - they feel deconstructed with a post-rock feel that throws of some of the shackles of song-writing convention.
Very good stuff anyway. Thanks to @PaulCarvill for the tip.