I will start with the positives. A huge library of both pay for patterns and free patterns. I place to store your project notes. Forums to communicate with groups of people who have the same interests.
I will now move on to the negatives. Over the years, Ravelry has practiced its free speech by posting very polarizing content. I believe this encouraged strife, though most (not all) stayed silent. Ravelry then decided that it could dish it out but could not take it. Ravelry updated their policy. It basically said that if you are not on their side then you either keep your mouth shut or be banned. Though many had kept their mouth shut, for the sake of peace, have decided that this was going too far. I deleted my account.