This movie was a perfectly timed lesson in life for my daughter (5th grade) going into middle school next year. After the movie we talked about the pressures of growing up, multiple teachers, people she has never met, changes in her "circle of friends", and life in general. I can recommend it for that reason.
It was well written an acted, although a little different from the book. The changes were just what Hollywood always does to a written work, amalgamate characters into a single actor. Simplify to fit into 2 hours. Emphasize action over character development. Still the essence of the Wimpy Kid's life was there for myself, and more importantly for my 10 year old daughter.
Go see this with your kid, have a pizza and talk about middle school.