Yes it's valid. The changes are quite few and little. But from many aspects, it can be said that it was a preparation of 1965 Missal, which was a prepartion of NOM in 1969.... Just like the Pius XII reforms of the Holy Week and other few points were made by Bunigni, who next made the NOM...
In the SSPX, the edition which is currenty used is the 1962, but this application dépends of the countries and of the priests.
I think you can listen to thios video, it contains somes aspects relevant for this topic and it's very interesting...