Though I defended Haitink's early recordings, I just realized that I have no other recordings by him, other than his original Mahler boxset and the Christmas concerts and a couple of the BPO Mahler recordings (and one Bruckner symphony). I still consider him an important Mahler pioneer, in that his was one of the first complete cycles to be recorded. However, I cannot think of any other composer, or period in which he specializes.
Aside from his Mahler recordings, I guess I just regard him as a competent conductor, but one who seldom produces a definitive or "great" performance, sort of like, say, Eugene Ormandy.
I still do not grasp the concept of his RCO recordings being good in spite of Haitink.