It's currently safe to use Spine editor 3.1 and use the current Spine-Unity runtime. I'd personally call that the "best".
The new feature in 3.1 (LinkedMeshes) should just be ignored by the loader if you use JSON, but loading will break if you use Binary.
3.1 for Spine-Unity should be ready this week though. It's a pretty simple port.
07 Mar 2016 5:38 am
EDIT:
Rechecked SkeletonUtility. It actually should be ready to use.
SkeletonRagdoll is safe to use if you don't have negatively-scaled bones.
Updating the .unitypackage now with the latest fixes.
If you encounter any problems, let us know.