Realistically, I saved about $850 this year on parking alone, and $500+ in fuel because of the bus. The bus passes cost me $15 per month for a grand total of 180 per year, so I'm ahead of the game there.

My usual R/T to the bus is about 5 miles. My usual RT all the way to work without taking the bus is more like 30 miles. All in all I averaged about 16 miles of commuting and errands per work day, or about 9.5 miles per day (weekends, vacations included).