As others have said, it depends. I have a '12 EVSE that was upgraded by EVSEupgrade.com and it works well in my '13(with a 27.5a max built in charger) but the problem(not for me but possibly for some) is it charges balls to the wall, 20a at either 240v or 120v. If you have a 20+A circuit(preferably 30a) it works great but not everyone has a 30a circuit, especially @ 120v. It also has no way to limit charge current, it is what it is, oh and it has a L6-20 twist lock plug that I cut off and installed a L6-30. Now this same charger only charges 16a @ 240v and 12a @ 120v on my '12 because thats the max that car will charge but using it on a 27.5a Leaf results in the high charging current.
Also whoever is turning in their Leaf may(probably not but may) run into issues because the '11/'12 EVSE looks different than a '14. When I emailed EVSEupgrade about the high charging current using the '12 EVSE on a '13 they offered to re-upgrade my '12 for 1/2 the normal price($150) but I don't know if they offer that to everyone or not. With the re-upgrade they'd replace the L6-20 with a L6-30 and make it adjustable to 20a @ 240v and I'd assume 12a @ 120v like my upgraded '13 EVSE. I didn't do it because of the 12a 120v limitation, I like the ability to charge at 20a(actually 19a measured) @120v but you really need a good outlet/circuit or preferably a 30a circuit to take advantage of that.