As an Englishman I would find the word OK too non-descript. It doesn't really mean anything, there is no emotional pull to it. It is already used on command buttons as well (press OK to continue). How about the phrase 'Cool' ? Or a temperature scale (hot,warm,cool,cold,freezing etc).

Also it is worth discussing if there should be a negative version available (facebook don't have a dislike button for a reason), from a physiological point of view do you want people to see that if they post something see more they might get judged by the haters? Also, it can send out a negative impression of the content on your site to visitors.