Casro1709 Thanks for sharing your experience so far!
I dove in yesterday, and so far no issues. I did some tests in a new project and then converted a 4.2 project directly into 4.4. I did have to reassign a few Spine atlases, but I'm not sure if that's because of the conversion or not. All my Spine stuff is working in the project, at least for now... including layered animations, and some procedural animation using SpineBoneNode.