Originally Posted by Hymie
On bare drywall you should use a primer/sealer before you paint. On painted walls, premium 100% acrylic paints are self priming. The 100% acrylic resin seals the surface as the paint dries. I have used paint and primers in one ( Behr and Glidden ) And both seemed to cover very well and was able to do one coat. All depends on the condition of the paint you are covering.
I've made this point, that it "works" before, and people thought I was endorsing the paint & primer in one, so I'm trying to be a little more clear now.
So, Yes they will seem to cover very well. But in a year or so you will realize it's not quite as good as you thought. If you're flipping houses or doing rentals, IMO it's OK to be cheap and quick. Just know that you are being cheap and quick; if you're looking for quality, it's not available at HD.