I've decided to stop rating books on Goodreads. (I still intend to review, when the spirit moves me, but I'm borrowing The Story Siren's example and removing the star ratings from all of my Goodreads reviews.)
I began writing book reviews several years ago on Visual Bookshelf (now defunct - I moved to Goodreads a couple of years ago). Initially, I joined VB just to keep up with the books I read. After writing a few reviews, I found I liked doing them - especially for books I loved and wanted to share with others who might also enjoy them. That said, I've always been a bit too do-unto-others to be very critical of someone else's creative work, even before publishing my own. I decided I'd leave the bloodshed to those who don't have my hangup, even if that makes me look like I love everything I read.
In actuality, if I'm actively disliking a book while reading, I either put it back on my To-Read list (if I suspect my mood is the problem - and that does happen occasionally) or I remove it from my Bookshelf list altogether. There are too many awesome books in the world to make myself finish the ones I'd rather light on fire... and life is too damned short to spend my hard-earned free time writing reviews of books I wanted to (or did) throw when I finished them.
Under the best circumstances, a review spells out the reviewer's emotional reactions to a book, what the reviewer brought to the table when reading, what he/she was looking for as a reader, and whether or not that desire was met. As a reader, these things are what lets me know if I want to buy this or that book. Since I'm officially an author now, reviewing-not-rating also dissolves some of the conflict-of-interest issues and frees me to (hopefully) write reviews that are as gushing or critical as I want (and yeah yeah, the latter will never be all that harsh because I'm a frickin marshmallow).