I read it! I read it in English class last term. Frank McCourt used to teach in my school. Maybe that's why the English department likes it so much.
As for my own opinions, I think it's written well, and there's a hopeful note in it. They say there's a sequel, 'T is, but I don't want to read a sequel; the first is always better.
Among the many things I liked about the book, one is worth mentioning. It conveys the message that it's good to have a better-quality life. When we were reading, a girl in my class told us about how, in the Soviet Union, people wanted to go to America because "even the poverty-stricken had running water." Well, here is the same attitude: if one compares the McCourt's poverty level in America and in Ireland, it's evident where it is better to live in poverty.
It has a positive outlook in general. Some memoirs I read are all complaint. This one is narrative.
Suggested reading: All Over But the Shoutin', by Rick Bragg.