US launch details for the Galaxy S 4 are arriving at last, and both Sprint and T-Mobile are on the vanguard. The two carriers plan to sell Samsung's flagship for $150 in 16GB form, albeit with different pricing strategies: T-Mobile's plan includes its now-standard device payment installments, while Sprint is discounting the phone from its normal $250 price through a $100 instant credit for those switching to the network. Just when you'll have the chance to plunk money down also varies. Sprint plans to offer pre-orders starting on April 18th, with an actual launch on April 27th. T-Mobile isn't giving customers the same opportunity to buy in advance, although they will get to take the Galaxy S 4 home a few days earlier, on April 24th. We're still waiting on other American carriers to hop on the bandwagon, but we suspect it won't be long.