Now through April 21st, any AT&T customer who purchases a Lumia 900 will receive a $100 rebate from Nokia -- effectively making the device free. The move is ostensibly a goodwill gesture from the Finnish manufacturer, which confirmed that a small number of early Lumia 900 handsets shipped from the factory with faulty software that caused memory management issues. It insists this problem is now fixed, and that come April 16th, all affected consumers may swap their device at any AT&T store or merely download the update. Previously, AT&T had announced a $100 mail-in rebate for new subscribers that'd purchased the Lumia 900, but thanks to Nokia, it's now effectively free for all. You might wanna jump on this one.