My Take
It's a great teaching tool. I like that kids can read others' opinions on books as well as write their own.
This helps them think critically and analytically about what they have read.
How I Use It
I have used Goodreads for finding reading and grade level/high interest books for students of all abilities. I believe that student choice drives engagement, so I have used it for whole class as well as small groups to decide on books for their study. It is a great resource for individuals as well as choosing titles for reading for enjoyment. I didn't find any downfalls to using Goodreads.