I purchased the extended service warranty to extend the coverage by 2 years/50,000 miles (up to 100k) for a little less than $2000. My car was purchased in July 2004 (04 2.5i with about 45k on it at the time). They told me that purchasing the coverage was cheaper than paying for the 60k and 75k check ups individually.
I just wanted to not worry about any service related issues for two more years after having a few minor issues taken care of during the first four.