Since you asked, I just completed an exhaustive renovation of my dining room ceiling where I removed the popcorn texture and added faux beams and custom crown molding (see the link). So, as to your question, "how much 'perfection' should I expect in a smoothed ceiling finish?" Remember you are talking about the ceiling and few people really notice/view/stare at what is going on with a ceiling. In my renovation, there are many areas where I did not sand the ceiling perfectly smooth after I scraped it. Flat paint works wonders for hinding all of them. What I would expect is that any imperfections not be noticable to the average guest who visits your home. How much wave is present? Fixing that would likely involve removing the sheetrock and sistering framing to the existing rafters to make them straight, then replacement of the sheetrock, etc. - a significant job in my mind. It just depends on what makes you happy and how much trouble you want to go to fix the concern you have. Here is a link that might be useful: Custom Crown/Faux Beams

Breezygirl, this does help since one of the reasons my kitchen was going to cost so much was because I wanted to remove the empty soffit and install 36" cabinets with crown molding. Most stores wanted to then remove all the popcorn first in all rooms downstairs telling me they could not patch it up. My most recent quote was in January 2014 and the contractor was going to put a beam to separate the rooms which I did not like as he said he had to remove the popcorn. I prefer no beam and to have just a straight line with the other room having popcorn if it costs too much to remove. I will try to take a picture of my kitchen. I love my tiles and it is helping to see that BM Simply White looks best with my tiles. I am going to put the recessed lights in my living room which is my home office and leave the fixture in the dining room part of the home office. I will then see if that room becomes a mess (has no lights in the ceiling now) before seeing who can patch up my ceilings. I will revisit my kitchen cabinets after the lighting is done downstairs, my wood floors are installed in the other three rooms to close out my insurance claim and my windows and doors downstairs are replaced as the vinyl has cracked and it is cold in the winter time. I really want kitchen cabinets and a counter like Breezygirl. I needed tiles due to little dogs going in and out the sliding door in the kitchen and having a KitchenAid dishwasher that will be 5 years old at the end of October with now poor reviews of a failing pump. I can't afford another insurance claim for my wood floors. I am only using the dishwasher if I am home. I paid a lot for this dishwasher.

Could that ceiling be painted it with a oil based paint. Does the paint on the ceiling seem different than the other rooms? My sister needed to paint a popcorn ceiling in a room with a roller. She was afraid to because we helped paint my other sisters popcorn ceiling and it turned to mush and started to fall off. (we figured out later that it was the technique used on hers that made it difficult, ground up drywall mush sprayed on) The paint store guy recommended to first paint with oil based, it will seal up popcorn and not "dissolve" what is now there, then paint with a ceiling flat paint after priming with oil based. I would imagine if someone wanted to scrape off the popcorn on her ceiling it would be a real mess because of the oil based primer.

Even professionals do not do a perfect job. If you wore the correct respirator, and have cleaned everything up correctly, you now have a house without friable asbestos in the ceiling. Get a test if you want. "Background" air tests are known to have come back positive even when sampled from outside.