In Illinois, I can pay $101 per year for a standard plate, $195 to register then $114 per year for a vanity plate, or $18 a year for an Electric Vehicle plate. Big surprise, I chose the latter. Not against vanity plates necessarily, but it's never been my thing.
Our EV plates are very plain (black letters on white plate, missing the Lincoln profile that graces standard plates here in the Land of Lincoln), but fairly identifiable with a consecutively issued number followed by "EL". Since we don't have CARB-type requirements for manufacturers here, there aren't too many EV models on sale. But we do have a pretty good state rebate of 10% vehicle purchase price up to $4000, so I think we're up to about 1700 EL plates by now. I'd be surprised if more than 15 belong to FFEs. Mostly LEAFs here, followed closely by Model S. Volts don't qualify for the plates though they qualify for the rebate. Funny.
The only problem I see with a very identifiable plate like a vanity or our EL plates is that they're probably easier for the speed cameras that have sprouted up in Chicago to catch accurately.