It looks like Sprint really wants your business, to the sum of a potential $400 in-store credit to be had for activating three lines on their Everything Data Share or Simply Everything Data plans. Said credit is then to be available to use towards the purchase of "qualifying devices," whichever they may be.
A 2-year deal will be required -- as you would expect -- and all lines must be active a minimum of 60 days. The qualifying period is set to start in stores only tomorrow, Aug 19, running through September 15.
As with all offers, there looks to be some fine print, a few caveats. Qualifying devices appear to be only phones. Tablets, accessories and portable hotspots look to be right out. And, if the device you're getting using the credit is eligible for a mail-in rebate, you won't get that on top. Can't have everything, after all. The credit has to be used in full at the time of purchase too.
The definite catch though, is that one line must be transferred from another carrier, and one that isn't affiliated with Sprint such as Virgin or Boost Mobile. Sprint definitely wants your business, but they also want new business.
All this comes from a leaked flyer, so it's not exactly 100% concrete. But, if it sounds like your kind of deal, maybe head into a local Sprint store tomorrow. See what's going on.