We had a site that was hacked on MT. The hack inserted files that gave the attackers an admin like interface to manipulate things. The files also had permission and user that matched the MT web server (different from the user and permissions we had on our files). A couple of days after reporting this hack to MT (less than 2 weeks ago) they did a forced database password change on all of their grid service clients. I'm certainly less confident than before about them but I'm not sure who you can really count on. Even high priced options like Rackspace have had issues.