Amazing, I love them. Really does help with getting the glutes to fire in the hole. Helps with learning how to get out of the hole properly too.
A lot of it's mental so once you've done the first set you know what to expect on subsequent sets. I've experienced the same with static squats on Mondays when I've followed Bill Starr's 5x5.It's weird how the first 170 set was the hardest when I think back.