I saw them live in 2004 at Austin City Limits. That was in the midst of their huge popularity surge and radio craze.
I don't know if Brock was sick or what, but it was the single worst show I have ever seen. They sounded terrible. The vocals were a mess.
On a more positive note, My Morning Jacket played minutes later and proved why they're such a great live show. I introduced several friends to them who are now big fans. Concert redeemed.