I don't like it when people rate books before they have read them on Goodreads.
The whole point of rating a book is to give other people a sense of what you thought of it, even if you aren't the kind of person who likes to write reviews for whatever it is you like to read. But if you rate it before it's read, it's a false opinion. To me, it's like lying. I understand that people get super excited for sequels to their favorite series that are coming out; believe me, I get so excited sometimes I practically vibrate.
Besides, what if the book comes out and you decide that you hate it? It would look really weird if for the longest time you had rated a book five stars and suddenly it dropped down to one or two. This habit is almost as annoying as the option to give reviews a 'thumbs down' or whatever on Amazon and other sites. Honest reviews of books are voted down by rabid fans, and it's just frustrating.
When I look at a rating or a review of a book, I want to see all different kinds of opinions. Because those things will help me decide if I want to buy it, or if I even want to read it. Honesty is important, and not everyone is going to love, love, love a certain book as much as others.
Aaaaaaand, that concludes my first mini rant. :)