MATE 1.6 is getting closer as some of the core modules has been bumped to 1.6.0 release on their GIT repository. The roadmap indicates that most of their TODO list for 1.6 release has been completed and the rest is a minor task to do. We should expect a MATE 1.6.0 release on April.
I have been working closely with Chess Griffin to bring MATE Desktop 1.6.0 for Slackware users in our MSB project and we are preparing to test the upcoming 1.6.0 release when it's released.
I have personally prepared two virtual machines which i installed Slackware-Current and Slackware64-Current on it. Both are updated with the latest patch and update from Pat.
So far, the basic desktop has been quite stable, with some minor problem as noted in the KNOWN ISSUE file. I really hope that MATE Desktop will bring another great experience for those who liked GNOME 2.