Today Eurogamer posted an article looking at the technical side of the FFXIII demo and discusses how the game would run on the X-Box at the time when the demo was created. If you are one of those who concerns them selves with frame rates, graphics and so on then this is a worthy read.
http://www.eurogamer.net/articles/final-fantasy-xiii-how-will-it-work-on-360-article
...and this is what the packaging will look like!

http://www.eurogamer.net/articles/final-fantasy-xiii-how-will-it-work-on-360-article
...and this is what the packaging will look like!