I'm fascinated with how the pitch clock will work in reality. There are a few specific areas of interest to me.
The exact moment of starting the pitch clock is open to interpretation. Is there going to be home-field advantage to exactly when it begins? The ump can overrule the visible clock, but are they going to note when it begins each time? That is probably intended to be more of a courtesy by giving a slight buffer after reaching zero.
How does rubbing up the ball every time a pitcher gets a new one work? It has been widely reported that the umps have stopped doing this pre-game as they are supposed to. Supposedly delegated this to clubhouse attendants who may or may not do so, which has led to pitchers complaining, possible sticky stuff increase, etc. Even pitchers who work fast, take well over 15 seconds after getting a new ball.
What about the mechanics of pitchers in the stretch? Aside from the pickoff issue, many pitchers have a very complex motion before slowwwwwwwly coming set. Even without the cat-and-mouse game of holding the ball to try and freeze the runner, some of these pitchers will need to adapt their mechanics.
Shaking signs off? Is there going to be a significant increase in trust of the catcher's signs? Does this put more value on a catcher's game-calling ability? Steals are expected to be up, but good pitch-calling may have even more value than ability to throw out runners. I like the increased efficiency of the audio signs, and that seems to have been a fairly important step prior to implementing the pitch clock. I first noticed sometime in the Varitek era that catchers seemed to be micro-analyzing each batter's stance and positioning before even putting down a sign. That has been lessened with the new tech this year, and will not be possible going forward.
As always there will be players who prepare and those who don't. I'm eager to see the effects of what else may change.