I'll be the first to agree that there are many good paints out there and a lot of bad ones. My last interior painting was with Benj. Moore Super Spec and I have really been pleased with it. I was really impressed with the fact that I had almost no little paint dots on my glasses after I had rolled the room. This has always been a good sign to me that it is pretty good paint. Poor paint leaves so many little dots that it gets really hard to see around/through them. I hear that it is just clay that makes the paint like this but whatever it is, it really helps. Thick paints really help in doing things like the mullions on multi-pane windows.
For what it's worth, check out the UPC codes on paint bought in a home center and the same brand bought at at an independent paint retailer. The codes usually are different. I have heard from many souces that this is what differentiates the lower cost and lower quality paint that the big home centers buy so they can "pass on the savings" to their customers.