I received a postcard from Navy Federal saying they are upgrading my card to a signature and will receive in two weeks. I went online and everything looks the same. Anyway, this is my first signature. Don't know exactly how it is different but it sounds good..lol
I have had it since July 2012.
Visa Signature gives you access to some perks. I can't recall off the top of my head which specific perks are available to NFCU cardholders (or maybe its automatically all of them?) but click here to see a list of Visa Signature perks.
The signature is not much different, but you do have a conceirge and some other benefits as described above...
The card design on the signature is way cooler than the original "greenie"