Every few years, there's an oft-uttered term in MLB sure to spark discussion, opinion, and sometimes controversy. Back in the 1990's, it was "salary cap". Later, it was "realignment", gradually succeeded by "revenue sharing",  "steroids", and more. 
The hot topic at present: "pace of play". 

"Pace of play" and "time of game" are used interchangeably, even though they don't necessarily mean the same thing. Some three-hour games are full of excitement and leave the paying customer wanting more. Some 2:40 games move glacially and are torturous to sit through.
Two years ago, before the "one foot in the batter's box" rule took effect, I watched a ton of major leaguers at the plate, as many as I could throughout the league. Too many dudes were dawdling in the box, adjusting this, re-adjusting that, staring into space, breathing deep, etc before practically every pitch. and I was going to call them out on the popular forum I wrote for at the time. 

It's one thing for a superstar like Derek Jeter, David Ortiz, or Ichiro to carry out their regular routine before a big at-bat. It's another for Ed Lucas to waste everyone's time psyching himself up on a 3-0 count in a game his last-place Marlins are trailing by 10.

Back then, Jay Bruce was one of the worst, if not the worst, box dawdlers, in the game. After every pitch, no matter the situation, an invisible hook not unlike that of Sandman would yank Bruce out of the box and almost onto the damn grass. Then we'd wait for him to deem himself ready and walk all the way back to the box, at which time the catcher would START flashing signs. 

Bruce actually inspired me to do an extended (about six-week) study on batters' box habits around the league in 2014—who was basically putting fans to sleep by unnecessarily dawdling in/around the box instead of actually hitting? 
Obviously, in some situations a little dawdling is justified, even necessary, so I generally (but not fully) limited my info gathering to regular, low-pressure at-bats—obviously, one could understand Nelson Cruz needing a couple extra seconds to gather himself with the tying runs on base in the 9th, as opposed to Seth Smith leading off the 2nd inning essentially taking short naps between every pitch.

Also factored out of the study:
⦁    brushback pitches
⦁    huge swingthroughs (trust me, sometimes you need a couple of moments after these)
⦁    potential sacrifice/hit-and-run situations (batter would be looking to coach for signs)
⦁    questionable strike calls (I don't advocate/approve stomping around in protest of a call—cough Angel Pagan cough—but for this type of study, we'll cut some slack)

In the end, I got ample data for about 250 veteran (or "established rookie", if there is such a thing) players. And by ample, I mean at least two at-bats in regular, low-pressure situations as described above, preferably over multiple games but not always. I noted their responses to balls and strikes separately.

The surprising results of the study: far fewer Jay Bruce-types in the league than I expected. The majority of dudes do what they do now: step one foot out of the box, pause, and reload. The percentage of dudes who stay firm in the box throughout the at-bat, as Barry Bonds used to do? Small, roughly 10%. Leonys Martin, Ben Revere, Josh Reddick, Nori Aoki and Rajai Davis were among the group.

Aside from Bruce, noteworthy dawdlers included Stephen Drew (who would tap each cleat and turn down the first base line), young Roughned Odor, Will Venable, Chase Headley, Austin Jackson, Brandon Belt, Adam Lind, and Brad Miller. These are the dudes who'd wander out of the box, practice-swing, practice-swing, glove-adjust, glare at the bat, sigh, dig in the box, stare off into space, then face the pitcher. This could drag on up to 25 seconds sometimes...a bunch of Nomar Garciaparra's. (Note: Never thought I'd have to differentiate between Nomars...wasn't going to write "Garciaparra" initially. Thanks, Mazara.)

Today (2016), while the pace still lags in other areas, for the most part the batter's box rule is effective. For the past six weeks I've been surveying major leaguers again, in an effort to determine if MLB's financial penalty for habitual box dawdlers has had any impact. While parts of the game (cough, replay, cough) often fall far short in the promptness department, box dawdling is dramatically improved (based on my limited sample size). Study B followed the same criteria as Study A.

The result: almost no one steps completely out of the box anymore save for the situations laid out above (big swingthroughs, brushbacks, etc.) The majority of dudes toe the box line between pitches; just about all of the others plant roots in the box upon entry (a small bunch leave the box so briefly and innocuously, to hold it against them would be anal and stupid—they're not seen as violators, at least to me.) The young kid from Atlanta, Dansby Swanson, is an egregious exception—his habits were absolutely painful to endure; he dawdled and lingered between literally every pitch. Ironically, he stayed in the box upon calling time-out! Likely the noob just needs time in the league and a couple ump rebukes to adjust. 
In one at-bat, Jake Smolinski of Oakland did not leave the box, but considering the length of time he tranced there between pitches, he might as well have...another painful at-bat. Miami's Dee Gordon also stepped fully out between pitches, but he was graded post-suspension and may have just forgotten the new guidelines. Or maybe he just doesn't give a s---.