I did it, killer deal.
But,... I assumed I would be installing through Origin. Looks like you need a gamestop specific program to install/play/run the game due to how gamestop operates their download setup. Will report back once installed.
Update:
Ok, so the gamestop app is needed, but it is used to procure the Crysis 3 gamecode that is then used to activate Crysis 3 using origin. This rather than gamestop just emailing you the gamecode... The gamestp app is still needed, and by default will load on Startup and bug you with advertising, but after activation on origin the gamestop app can be deleted and/or only used when more deals are found on gamestop.