Wired's interview gives some of the history behind the 3DS.
http://www.nintendoworldreport.com/news/23699
During E3, Wired's Game|Life blog interviewed Hideki Konno, Head of Nintendo's Entertainment Analysis & Development, Software Development Group 1. Konno has worked on Nintendo games since Super Mario Bros., and more recently was the producer of Nintendogs and Mario Kart for Nintendo DS. He is in charge of the concept and definition of capabilities for the Nintendo 3DS.
The interview confirms several details about the 3DS hardware and software, including the existence of downloadable content similar to DSiWare, a Tag Mode viewer for data saved from games supporting Tag Mode, and that the shape and look of the 3DS are the final version and are not expected to be changed before release.
On the inclusion of the Slide Pad, Konno notes that both he and Miyamoto insisted that the next handheld console included analogue control.
The full interview is available at Game|Life.
Wired.com: There’s an accelerometer and gyroscope in the 3DS. Does that mean it pretty much does what the Wii MotionPlus does?
Konno: Yes, the same type of motion sensing is possible.
