I've found it really frustrating that the invert buttons were missing. Previously, I had to manually copy a vertex group and invert it in Weight Paint.
That workflow has proven to be pretty destructive (if new verticies are created, they aren't included in the manually inverted vertex group and you had to go through all inverted groups you manually created and redo them for each modifier).
I hope this gets accepted because it will really speed up the workflow for that node.