It is a very messy process. Depending on how it was originally applied it may be faster and cheaper to cut out the existing sheetrock and replace. If the popcorn can be scraped you will still have to float out any "waves" in your structural framing. any texture in drywall can hide a lot of imperfections. In any instance you'll also need to prime, paint, and possibly put a light knockdown/orangepeel texture. Not as easy as one may seem. It will be well worth it. Always cleans up the space and seems to make it more inviting! Hope this helps!
Trey