It's a good (long) insightful read, a couple of extracts : "There was no real brief on the mix. I was approached by Sony Records. Usually when you’re doing a 5.1 mix there is no brief...
The thing with 5.1 mixing is that you have so much space to fill that I probably found myself adding a little bit more effects to do that than they did in the original stereo mix. There’s so much of a stage to fill out on the 5.1… so rather than just put ambience in the back speakers and the band in the front—like a live performance—I tried to spread things around a little bit more."