For US properties 98% of the time they post correctly. In the UK and Europe 30% of the time the stays do not post or they only give you about 80% of the points you are due. Asia about 90% post correctly. That has been my experience.
Starwood or Hilton I have never had a posting problem, but I give Marriott 98% of my biz, so maybe I would see the same problems with the other chains if I had enough stays.