I think there is a lot of value in hitting balls at a faster rhythm.
First, it will give a better feel about how much of the shot clock one is actually using if they play tourneys where that matters.
You have an internal clock, and they give you a warning.
Second, it can be beneficial to figuring out how many shots were actually taken, a person will know after a session whether they were close to their fast speed or not.
Don't see any benefit to being at a fast speed, but do see a lot of problems with it.
Third, I don't believe in needing to practice perfection on every shot. There is a lot of value in pushing oneself in a practice session, what Cardigan did here was likely to put a certain pressure upon himself that he probably doesn't usually get while practicing alone.
If you don't practice perfection on every shot, you will never come close to achieving it.
Tied into the third point, missing can teach one as much or more than pocketing if a person is willing to figure out why he missed. I usually want to play as much as possible when my game is off precisely because I believe that my 'slump', as some would call it, is me being on the verge of learning something new. Thus, I want to be at the table as much as possible.
If you practice perfection on every shot, you will train yourself properly, and you won't have those slumps at all. Slumps are not being on the verge of learning something new, but rather are just the result of doing things wrong from what you have been doing.
Finally, when I play at a fast pace, I don't notice anything but the table. Whether it is because I am playing fast that I don't notice things that aren't at the table, or if it is because I don't notice things that I play fast depends on the situation. There have been times when I didn't notice anything but the table and the shot where I found out that I have played fast. There are other times where I forced myself to play fast so I could tune everything else out. It's amazing what a heightened level of concentration is capable of allowing.
A heightened level of concentration should always be strived for . Playing fast is one way, but is wrought with peril.
I read about a study once where they studied the effect of speeding up the pace of a task. They had people who were proficient at the task and people who were newer to the task. The newer people saw a huge drop-off in their performance when they were forced to speed up. The proficient people saw almost no change in performance when they sped up.