Prices are brought closer to world levels, improving trade negotiations with other trading blocks. World farmers will benefit from higher prices and being able to export more to the EU
Consumers will pay lower prices.
Better for the environment because set asides are encouraged and intensive farming discouraged. Farmers are rewarded for considering the environment this is an important issue in attempting to overcome market failure in farming which used to occur.
This is very important with the expansion of the EU into the East, many E. European countries have large and inefficient farming sectors therefore reform of CAP causes greater urgency.