as other users have said its a natraul progression of the tile system and makes sense to me , you look at a cube head on its a tile , now the user could press the tile and then spin it for more info of the app or to enter a different part of the app , if you think about it , this could be used quite effectively and still be polished and simple if done right and wouldn't be moving far away from the ui now but adding more to it like apple have done over the years with ios etc
as other users have pointed out a cube has 6 sides so if an app is programmed to use the cube tile you could get 5 more functions out of a tile , 5 more shortcuts out of one tile would be very effective if done right and like I said it offers the o/s more functionality , it would be a bit like sailfish o/s and the way open apps can be interacted with on the home screen , sailfish only supports 2 methods with interacting with an app this new cube method could present a total of 6 interactions with an app from the home screen ...... seems great to me ;-)
greedypnguin I am sure you would have to interact with the tile before spinning it to prevent accidental spins of the cube , a simple 1 tap to activate tile then spin to use cube then press to enter the cube section you want would work well and avoid accidental spins ;-) all that would change is if you want to enter the 1st screen of the cube like you would a tile at the minute you double tap that tile ;-) this way you wouldn't even have to use the cube system if you didn't want to and could use it like normal windows 8 ui like you do at the minute but just double tap the tile to open it or single tap and spin it , it offers users who want more exactly this and users like who who don't exactly that if you think about it buddy ;-)