Up here at the FM world headquarters, I've recently pushed the buttons and typed the commands to make $acorn$ 5.6.4 roll out to all my favorite people.
It's purely a bug fix release, but it includes a fix for a 10.12 issue that I've spent way too long tracking down. So if you're on 10.12 Sierra, and you've seen the occasional case where a black box would suddenly appear somewhere on your canvas, this release is for you.
So start your update engines and grab it today.
And a small request: if love Acorn and you've purchased it via the App Store, why not leave it a nice review or give it a handful of stars? When we push out new releases, it resets the previous reviews and ratings in the store which is a huge bummer for us (and it also creates a disincentive for releasing bugfix builds! But that's a story for another time). We love getting reviews and ratings though, it's like fuel for future releases.