From what I understand it takes at least 100 hours to finish the mud portion of the top kill, so calling it a failure now cannot be supported; Glennage is clearly mistaken.
The drilling mud is nasty stuff however:
http://news.discovery.com/tech/how-bps-top-kill-will-work-we-hope.html
http://www.formatebrines.com/
Water or oil based, it usually contains Barite, or Cesium.
Hayward stated they are using a water base, which means that it is likely this mud:
http://www.freepatentsonline.com/3962099.html
It's nasty stuff, but compared to at least 11 million gallons of crude and over 600 thousand of dispersants, if it works, it would be worth it. If not, it'a 50,000+ pounds of toxic and sometimes mildly radioactive mud.