I did enjoy Christopher Howell's recent review of the reissued Neumann Dvorak cycle on Supraphon. Nice to get some historical perspective.
I just want to point out that his quoting David Hurwitz as saying Neumann 'in general had a tendency towards “a certain stiffness”' is incorrect.
Hurwitz used this expression only in his review of Neumann's CPO Mahler cycle. What he said was "Neumann’s interpretations of these works vary markedly over time, and if he had a fault, it was that he sometimes showed a certain stiffness of tempo...". (see link)
In his review of Neumann's digital Dvorak cycle Hurwitz says: "His principal weakness seems to have been a sort of stiffness that could on occasion paralyze his ability to make the music flow". It is clear that he is referring to Neumann generally since he goes on to say that the Dvorak cycle is not affected by this weakness. As a result of chasing this up I've now read Hurwitz's enthusiastic review of the analogue cycle, where he makes no reference to this general criticism of Neumann's work. As far as I remember I've never read Hurwitz's review of Neumann's Mahler