CREDO Mobile, a reseller of Sprint and a MVNO (Mobile Virtual Network Operator), have got hands on their first Windows Phone, the HTC Arrive. The Arrive features a 3.6" screen, a vertical slide-out physical keyboard, 16GB storage, Windows Phone Mango and is a decent first generation handset. New customers can get the device for $199.99 on a two year contract. Best of all, it'll have all the Mango improvements on-board.
Source: CREDO Mobile, thanks Mark for the tip!