New developments about open separation are discussed. Three-dimensional separation in general can be identified by the convergence (or running-together) of the limiting streamlines in spite that this procedure does not answer all deeper questions. An open separation is shown to start from a regular point in the middle of the surface flow field, this idea is in direct contradiction to the conventional notion of separation and has been a stumbling block for many to accept the open separation concept. The streamline vs. envelope debate remains unsettled even though there are researchers who changed their preference from the envelope to the streamline version. Criticism of open separation is replied in details. Tobak and Peake reversed their previous stand and came to a position essentially the same as ours except in terminology. Cebeci, Khattab and Stewartson objected to our open separation idea on a superficial ground even though this very idea has been supported by all related experiments and calculations. In contract CKS' suggested alternative is a mere speculation with no evidence. Finally the open vs. closed separation concept can be carried over by analogy to unsteady cases.