As far as I'm concerned, Jónsi is the reason for Vibration Reduction (Image Stabilization) technology in photography exists. With the extremely low light and low level of movement in the singer, this show was the perfect – and necessary – setting for better shooting through technology.
Jónsi's show is dark. It's really dark. Think ISO 6400 and 1/30 for the opening song at f/2.8. The second and third songs are brighter, but only by a couple stops. However, the beauty of this show is that it's the perfect setting for a lens like the Nikon 70-200mm f/2.8 VR.
The saving grace for how dark it was very often at this show was that Jónsi's not moving that much while he's softly rocking the mic, so I had no hesitation using slow shutter speeds like 1/30 or 1/60 on the 70-200mm telephoto. Thank you, VR!
While I don't always recommend buying Nikon VR or Canon IS for concert photography, they do have their place. For most rock shows, you're never going to get their full benefit, because VR and IS lenses only compensate for user camera-shake – they're not going to be useful for preventing blur in a frantic rocker.
Where VR and IS do come into play with music photography is for more stationary, lower-key performances. Think acoustic, solo singers, prolific musical geniuses from Iceland.