If you are thinking to buy a premium smartphone from sometime, waste no time and buy the Galaxy S6. As the phone is SIM-Unlocked, you can use the phone on any carrier of your choice. But keep in mind that the phone will only work in GSM carriers like AT&T and T-Mobile not on CDMA networks such as Verizon.
Also the seller mentioned that the phone is available in limited stock. Order the phone before the offer expires.