For 50 years, home air conditioners have used R22, and it works great. But R22 is an HCFC: a hydrochloroflurocarbon that does have some effect on the ozone layer. As of the year 2010, new units will not use a HCFC as a coolant.
R22 will still be manufactured until 2020 (with substantial production cuts) and be available in recycled form until 2030. As you might expect, the price is rising.
Today, all manufacturers are switching to R410a, which is an HFC which has no chlorine. R410a works well in residential equipment, but does have some drawbacks, mostly evident in a poor installation. As it becomes more prevalent, the prices for R410a are dropping.