We are using Sequelize.js in our Node project and I guess it kind of does the job done but there are gotchas. One example is that the MySQL Sequelize query engine does case sensitive string matching on the SQL string that you feed it (this.sql.indexOf('SELECT') == 0). This means it can fail if your SQL happens to be lowercase. SQL keywords are usually case insensitive (although upper case by convention) so the Sequelize implementation seems like a hack.
There is migration support in Sequelize as of version 1.3.0 but I haven't used it and I'm considering rolling my own instead.
I come from a background of having used the Ruby ActiveRecord ORM and in light of this and the gotcha mentioned above I'm hesitant to recommend Sequelize. Unfortunately, I don't know what better alternatives are out there.
UPDATE1: there are other ORMs suggested under "Which ORM should I use for Node.js and MySQL?".
UPDATE2: I've released my Sequelize.js migration code on Github