Constructive criticism - Gus and the Sabbath tunes
From the clips I've seen so far on YouTube from the Scream tour, Gus does a nice job with the Randy & Jake era chops. For the Zakk stuff he sounds like a guy trying to play like Zakk, which isn't a plus even though he plays them very clean.
My biggest gripe however is with how soulless he sounds on the Sabbath tunes. It's disappointing because Gus talks about how Sabbath was a big influence on him when he first picked up a guitar. I think sometimes the highly skilled, technical players get bored with the simplicity of some of Tony's chops because most are simple to play. Gus is forgetting to let the evil-ness of a single note of doom resonate and make your hair stand up, the way only players like Tony and Dime really know how to do.
My only advice for Gus on the Sabbath tunes, is don't flood us with fills. Let your single notes breathe, and make our hair stand on end at the ring out Sabbath's doom and evil. Go back and watch some of Tony's work on the Paris '71 set. That's what you want to capture. When it comes to the Sabbath material, you've got to play it legit...and the only way to do that is to slow the hell down and simplify it. Tone and tempo are everything. Feel the Evil & Be the Evil, Gus. I'll be watching you guys this Sunday. Bring the Evil.