I do this with iPhone (past and present 4, 5 and now 6), MacBook Pro, iPad.
Yes, charge time is much, much faster. But, I wonder how this effect long term battery life. Does it wear out the battery any sooner than the slow charging of the lower wattage chargers?
I replaced some duplex receptacles in my house with the new ones that add 2 USB charging ports to them. I plug in my iPHone, iPad and my wife's LG phone every night.
I know they are safe. But am I shortening the long term battery life?