Popular in the 70's as a way to shortcut finish work and save on building costs, popcorn ceilings are not the most aesthetically pleasing finish.

Many of the early spray textures contain asbestos which poses a significant health hazard for removal. The only way to know for sure is through lab testing.

A good site with more information on popcorn ceiling removal can be found at http://www.naturalhandyman.com/iip/infpai/popcornoff.html