Some of the mistakes i have seen this year are simply just inexperience or lack of attention. We for one have alot of umpires that are very young as in maybe a couple years older than us in some cases. I know for a fact a couple who graduated only 2 seasons ago. Im not saying this is a bad thing they just have to get some experince under their belts and the players, coaches, and fans should realize this guy is not as experienced and may miss a call or two. If it weren't for them we may have no umpires in the later years.
As for wanting the strike zone to be by the book. You really don't want to see this from letters to knees. For pitchers that throw harder they will live way up in the zone and batters either, one cant catch up with it so high or, two they will just pop most stuff up for easy fly balls. For the slower pitcher decent batters are just going to smash the ball. Perfect example is a game that was played last week. On Monday the strike zone was about from high shins to belt and the umpire did a great job staying with that all day, this resulted in a very low scoring good baseball game. The next day played with a umpire who was making the pitcher work from maybe mid thigh to letters. Let me tell you the ball was just being crushed. I personally as a batter and pitcher would rather have the low consistent strike zone than the high inconsistent one just for the fact it will be a better game and work both ways.
Over all most of the umpires have been alright from what I have seen this year. And we have to give it up for the veterans who I have played with for years and the young guys for taking their time to come out and officiate the game we all love.