I can't speak to the zinsser paint Howard, but I do like the BM Muresco (blue can with white lettering). I just burned through a couple gallons of it the other day. It seems to have changed a bit though. I noticed a slight angular sheen, but it's supposed to be a dead flat, and it was, before. I wonder if some of the flatting agents have been sacrificed to the idiot VOC gods. They do have a new waterborne ceiling flat, supposed dead flat, that I have used before. It's okay, but the price point is a little higher. Even BM Super Spec flat wall is good for ceilings. I'm generally not a fan of flat wall finishes for ceilings in general, because most flats have slight angular sheen, but SS flat is good. I'm a stickler for the flattest ceilings possible, and I also don't believe you need to go into the high 30's or 40's for ceiling whites.