FAQ discussing always-on and DRM. (Xbox link is broken, linked to Engadget for now.)
The official FAQ starts off with the "always-on" DRM issue and also addresses used games, indicating that the box is designed "so you can play games and watch Blu-ray movies and live TV if you lose your connection," and that it does not have to always be connected. That said, it still "requires" a connection to the internet, promising cloud-based benefits for gameplay and more. Other questions answer things like whether the new console will require more power (no) and will our Xbox Live Gold subscriptions still work with the new and old hardware (yes).
When it comes to used games, the FAQ's response is also promising, stating "We are designing Xbox One to enable customers to trade in and resell games."
Oh, and no chance at playing Xbox 360 games or even Arcade games. But the good news is your XBL profile and Gamerscore transfer. Phew.
the Xbox One will not play your Xbox 360 game discs, nor will your Xbox Live Arcade games transfer (not to mention any other content that's dependent on the 360's hardware architecture, anyhow). That Gamerscore you've been earning, though? That's gonna transfer. As will your Xbox Live Gamertag.
Sadly, due to the x86 architecture of the Xbox One, the PowerPC-based 360 titles simply won't run on the hardware. Microsoft's not super worried about consumer reaction, though, telling Engadget, "We care very much about the investment people have made in Xbox 360 and will continue to support it with a pipeline of new games and new apps well into the future," a Microsoft rep told us. That said, Xbox One is designed, "to play an entirely new generation of games -- games that are architected to take full advantage of state-of-the-art processors and the infinite power of the cloud."