A good step in the right direction. I look forward to similar treatment to the ticket system to provide real workflow and field customization would shore up one of the largest gaps in their product. If they combined distributed version control, tickets, wiki, and HTML5 offline browser capabilities, Github would be close to the perfect CM tool.
Issues isn't perfect. I dislike the way that the AJAX-y elements work, there's no "read all" button, sometimes I have problems setting colors and such, there's no way to attach a pull request to an existing Issue... but seriously, if I have to use something as complicated as Mantis or Rally to manage tickets, I just won't do it.
