Personally, I prefer the smaller model rockets, but there is a large group of rocketeers who prefer a lot more fire and smoke to their rockets.

Over the last 9 years there has been a major court battle over the use of APCP (Ammonium Perchlorate Propellant). The BATF (Bureau of Alcohol Tobacco and Firearms) classified APCP as an explosive. APCP is the fuel in the Orbital Shuttle's solid boosters. It is also the fuel used in most high powered rockets. Today Judge Reggie Walton finally handed down a judgment in favor of the rocketeers.

http://www.rocketryplanet.com/images/pdf/ATFE-03-16-09.pdf