You may notice a loose of power; over time, it may cause other driveability issues that may turn into serious problems. The code basically means the catalytic converter efficiency is lower than it should be. But this doesn't necessarily mean the cat is bad. First, you may want to check the oxygen sensor(s). This other post may help:
Inspect the exhaust system for leaks or similar problems. Then, have the cat check to make sure it is the problem. Hope this helps.