To add to things that make me cringe with younger pitchers. Kid just threw two fastballs that the hitter wasn't close to making good contact with... It's now 0-2... here comes the curveball (off speed pitch) not close to the zone... before you know it, its 2-2 or 3-2 and this hitter should of been attacked and challenged on the third pitch... sometimes kids get too cute with pitching... but i remind myself that they are learning.I would think that's generally true most of the time, the pitcher puts the ball around the plate and the infield defense is good enough, batters will get themselves out. Two things that make me cringe as an umpire: pitchers that can't throw strikes, infields that can't make routine plays (good ole "strikes and outs").
I think one of the least used combinations of pitches I see that is great is the change up after a curve ball/slider. A lot of younger hitters gear up for fastball after an off speed. A good change up there is a nice follow up to the (Curve/slider)