Slipknot was kick ass! They always put on a good show, and they utilized the entire stage at Verizon. I never realized it was that big! But definitely a show I highly recommend, even if you're not a Slipknot fan. They just do it.
Unfortunately, my ride got there late, so I didn't get to see Trivium. But I heard that they were great and kicked some butt. Wish I could have checked it out.