The worst that can happen if you plug your Quick220 into a GFCI is that it'd trip the GFCI circuit. You can use the included tester to see if it's a GFCI circuit or not (which does the test by tripping it anyway if it's GFCI).
If you find 2 out of phase non-GFCI outlets, the next worst thing that can happen is that if you have the Rev2 16A version of the EVSE, and your 120V outlets are 15A, you may trip the circuit breaker. Then you know and try to look for 20A 120V outlets instead. Or make sure they're 20A outlets in the first place to prevent tripping the circuit breakers.
At any rate, if you make sure you have 2 out-of-phase, non-GFCI, 20A 120V outlets, there should be no long term safety concern about using the Quick220 on those outlets to provide the 240V output for your Rev2 16A version EVSE. Of course you'd have to make sure the cords and boxes are tucked out of the way so people don't tripped over them walking around.
And of course if you have the Rev1 12A version of the EVSE, then it should work fine with the 15A outlets.
This is assuming that you buy the 20A version of the Quick220 that has the L6-20 receptacle (model A220-20L).
If the concern is having to plug/unplug to the outlets on a daily basis, you can just leave everything connected and the Quick220 will have an 8W standby draw and the EVSE will have a 2W standby draw. Or get a couple of switched 120V power strips. I was told by Duane of Quick220 that if you just switch 1 side of, the standby power of the Quick220 will be reduced from 8W to 2W.
By the way, to clarify, the circuit breaker switch on the side of the Quick220 does not turn on or off the unit. It only energizes or de-energizes the 240V outlet in case you want to prevent sparks when connections are made to the outlet due to instant current draw of the connecting device/load (which shouldn't happen with the EVSE). Duane said that it's designed to withstand normal switching several times a day and should last for years.
