You can now rate post. You do not see it in the quick reply but you can see it when you click on the post reply button. From there there is a question saying "What do you think of this post?". You then give it a rating. A bot (don't worry he's a cool guy) will state the action.
I may do more than that like if I see someone has given you a good rating, I'll reward points or experience or whatever.
I think that's pretty much it, but don't abuse it. Have fun!