I use Twitter a lot (90k Tweets, 2.1k followers, my account is 8 years old), the best thing about the like is being able to end a conversation without saying anything. Liking a reply to is a great way to say "I've acknowledged your tweet with a positive connotation". I think Twitter forgets that the vast majority of content on the site isn't heated political debates but instead small communities of people who treat the website as a microblog.