In my experience, the bus is never on time. However, because I am in a city, it tends to run every 10-15 minutes, so missing one bus isn't that big of a deal. Google has been nice for helping me get places in which I didn't know how or if I needed to transfer. It will give you directions such as "Ride bus 1 to this street, walk a block, then wait for bus 2". It has simplified the Public Transit process about as much as Mapquest* simplified getting from point A to point B in your car (before GPS was common). Sure, it can have errors, but more often than not, it's good.