If you consistently use a Top Tier gasoline, then you probably won't get much benefit from periodic fuel injector cleaner. However, at just a could of dollars every oil change, it seems like cheap preventive maintenance. When I was working at my parent's automotive repair shop, we had multiple customers return a week later and ask us what we did to their car besides an oil change because the car ran so much better. All we did was put a bottle of injector cleaner into the fuel tank, checked the filters and fluids, made sure the tires were properly inflated and checked all the bulbs. And before you suggest the real issue was that we replaced a plugged air filter in addition to adding the injector cleaner, that usually wasn't the case.
-Rod