I recently sold a home to that was highly upgraded but still had "popcorn ceilings". My buyers decided that
they wanted to have the acoustic removed from the ceiling for health and aesthetic reasons. As most people do they had a few estimates and decided on a painter.
My buyers had a vacation previously scheduled before they bought the home so their closing fell during a time that they would be out of town. I monitored the closing and accepted the keys on their behalf. I also extended my assistance to them in meeting the painting contractor. Here is where the problem began.
What happened next appeared to be a "bait and switch" situation. The painter gave an estimate to remove the acoustic, "popcorn" from the ceilings, re-spray the texture and repaint. Approximately 20 minutes after the painter began his work he told me that the ceiling did not have drywall and that it now needs to be patched before it is sprayed or else it would be uneven!
I could not believe that a painter that has been in the business for 10 years could miss something like this. He claims that he tested it when he gave the estimate but obviously not good enough! Now he was quoting almost double to complete the job. What makes this situation worse is that I could not get a hold of the owners!
The situation got resolved after several phone calls and intense negotiations. My lesson from this is make sure that whenever a painter is quoting to remove "popcorn" from a ceiling that they actually scrape an area of the "popcorn" off before they give their estimate. It is too costly of a difference in the the price when the ceilings have to be patched, sanded and then re-textured and painted!
Written By Tina Maraj, REALTOR Since 1989! www.TinaMaraj.com RE/MAX North Orange County 
Fullerton Chamber Member and Ambassador 2009
Follow me on Twitter http://twitter.com/Tina4Homes
Good advice Tina. Many of the homes in my area have these "feature" ceilings and if they're not done correctly the results can be bad. Of course the reason for the popcorn to begin with was so that the drywall guys didn't have to do great work with the seams etc. It is a problem!