facebook_me_gusta.user.js

// ==UserScript==
// @name Facebook Me gusta
// @include http://*.facebook.com/*
// @description Changes Like links to more appropriate "Me gusta"
// ==/UserScript==

Array.prototype.slice.call(document.querySelectorAll("button.like_link")).forEach(function (elem) {
	elem.querySelector(".default_message").innerText = "Me gusta";
	elem.querySelector(".saving_message").innerText = "No me gusta";
});