It's been around for a few years now. Games went from averaging around 3 hours to averaging 2.5. The long tail of 3.5-4.5 hour games were basically eliminated. The only time that happens now is if you get extra innings, high pitch counts, and lots of plate appearances that don't end in outs -- in other words, longer games are long because they're good!

Occasionally an old head will grumble about it, but even the old guys tend to be pretty happy about the pitch clock.