I have the same problem. The last update seems to absolutely have killed the performance.

Also, when clicking on a draw order key, the draw order view in the tree is not updated to match the current frame's draw order until a change is made.

Trying to help Nate get to the bottom of it:
Is it slow even when you have the Animations panel/Animations View closed?
Not Animate Mode. Animations View.

Very upset about the new update causing major lag and now it crashed for the first time ever. Very urgent fix needed!

Came here for the same reason.

Is there any way o rollback the update? I tried reinstalling but I got v.2.1.22 straight away, can't work like this.

I only have the tree open, it works fine for 30 seconds - 1 minute, then it starts increasingly losing frames until it becomes unusable or freezes.

I'm on windows 8.1

Sorry about that guys, there was a leak with the font rendering. Building 2.1.23 now with a fix.

A fix will be up within 20 minutes or so, but you can always rollback:
http://esotericsoftware.com/spine-settings#Version

Thanks! Was just wondering what the heck happened. Thanks for the quick response, as usual.

Yaaay thank you!

Thanks a lot Nate, you are a lifesaver.