Microsoft Offering $100 Store Credit to Exchange Your Tired PS3 for a Shiny New Xbox One
Microsoft's trade-in offer is available at select Microsoft Stores in the U.S. (including Puerto Rico) and Canada; it's not valid online. In addition to accepting PS3 consoles, Microsoft's promotion also includes Xbox 360 S and Xbox 360 E, the latter of which is a semi-recent redesign to make the last generation Xbox look similar to the Xbox One.
According to the fine print, trade-ins must be fully functional without any broken or missing components and include all original accessories. It also says that in order "to receive maximum trade in value, you must purchase an Xbox One at the same time."
Whether or not this is a good deal depends on the condition of your old console and how much you value your time versus attempting to sell it on eBay or Craigslist. You can probably command more on the second hand market, though that also comes with certain burdens and responsibilities, such as shipping fees, possible final sale fees, and potential customer disputes, to name a few.
Microsoft's Xbox One outsold the PS4 in the month of December according to data provided by NPD Group, though the PS4 is still in the lead. Sony recently announced sales of 4.2 million PS4 consoles around the world through the end of December, versus Microsoft selling 3 million Xbox One consoles.