The check engine light is part of a built in computerized system, so you should not ignore it. It is important to not confuse the check engine soon light with the service engine light because they have different meanings than the check engine light. The maintenance is required when a service engine soon light illuminates at a given mileage to let you know that a vehicle service is needed.
The check engine light is now required to monitor a number of different emissions factors, including the exhaust that comes out of the engine. It can even monitor the exhaust again as it is exiting the catalytic converter. These newer systems are so precise that the check engine light may come on if the gas cap is not tight enough. Also the light will come on if there is a leak anywhere in the fuel system.