After the new release of steemd, I have quickly updated and replayed my witness node to 0.20.6. It works well and I have already produced a couple of blocks with the new version.
Changes are mostly related to Resource Credits. One of the important change is that the cost of broadcasting custom JSON operations (except the Follow plugin: follow, unfollow, mute, reblog) decreased 20x.
This is good for the apps utilizing custom JSON operations, but do we need these tweaks on steemd's source code? Making these dynamic would be better in the long term with the witness participation.
See the full list of changes here.