Popcorn ceilings were put up for several reasons - 1) because it was just the thing to do back in the 70's and 80's, 2) bacuse the ceiling finisher wasn't talented enough to do a knock-down ceiling texture, or 3) they were trying to cover up a sin of poor ceiling finishing. Since then, people just have not wanted cottage cheese on their ceilings and most are done wiht a light knock-down texture.
Everybody here has been giving great ideas. I'd lean towards the light spray of soapy water over the heat-it-up process. As others noted, removing the texture may leave a poor finish on the ceiling that can either be addressed several ways. First, patch, sand and finish. This would be about a half day job by a drywall finisher or an extended project for an amateur like me. Second would be to put another layer of drywall over the first and have a new smooth ceiling to start from. But that would include removing most of the popcorn so the new ceiling sits level. Third would be to remove the whole ceiling - popcorn, drywall and all - and repalce with new. But remember that removing the whole drywall ceiling means that whatever is above it would come down too - insulation and other attic collectibles... I guess the last choice of buying a house without popcorn is out of the question...
Asbestos and Lead Paint may be a concern if built before 1980 as others mentioned.
Good Luck. Let us know what you decide.
jeff