I looked at the site but I couldn't find any explanation of why this exists when there is Linux Mint Mate.[1]
Regularly, they have some kind of update packs which they announce on their blog/forums, in case you should get any problems, and the community seems very nic. Definitely try it!
I'm somewhat wary of forks now. Deviating from the standard configs is asking for trouble when it comes to upgrading.
If I preferred MATE, I'd probably use this over mint for this reason.