Fantastic! Odd timing as well, as I just received an email from my daughter asking if I wanted to go to the King's Singers concert (they're coming to our campus next month) and she sent a Youtube that I had just finished listening to when I came to our site.
I've heard them a couple times in the past, once in Westminster Cathedral (talk about acoustics!) and at the National Cathedral in Washington D.C. (again, talk about acoustics!). I've never heard better pitch or breath control.
But that kid on the accordion sounding like E. Power Biggs on a major pipe organ doing Bach was incredible!