"As They See 'Em," a recently released book by Bruce Weber, is a superb account of what it's like to be an umpire. You should read it.
Unfortunately for the major-league umpires, however, folks in the commissioner's office have read it. And they are not pleased. According to multiple people in the loop, the already-frosty relationship between the umpires and Major League Baseball headquarters has taken a hit from the book.
In the book, multiple umpires voice their complaints about the way they're treated by the current administration. From the basic (not paid enough) to the more internal (favoritism) to the downright esoteric (the World Series umpires weren't featured in a recent World Series program), the umpires come off as extremely hardworking but also a tad whiny.