Visited the new Shake Shack at Suntec (1st floor, Convention Center side). Going just before dinner was great as there wasn't any queues.
Ordered the ShackMeister Burger (a cheeseburger with fried shallots) and fries. On first impression the burger looked small but once I sank my teeth into it, omg it was delicious. Easily one of the best fast food burgers in Singapore. (Ok, maybe at $10 it's not really fast food). Fries cost about $6 and it was equally delicious.
Overall not cheap, but worth it for a splurge once in a while.