I think the idea is that since all standard mains connected devices must be capable of operating with an input voltage of as low as 207v then you can safely drop the voltage to 220.
Safety is important and as you stated probably not an issue in itself. However performance of appliances and other devices might be, it really depends on the device. And it won't always save money. A cloth dryer might be one example. It will still take the same energy to dry a given load, at reduced voltage it will just take more time to dry thus not saving any energy at all. Lights as I said may be less bright and that may or may not be a issue. A vacuum cleaner may not pick up as well and it's never nice to piss off the person that runs the vacuum. 
Lefty