Not sure if this is common knowledge, but a few videos of Diamond/Pearl
being played exists.

http://www.youtube.com/watch?v=1lYGiX2UuTg

Standard world-explroing stuff.  Personally, I like the music here.  Nice to
see images in action as well.

http://www.youtube.com/watch?v=GmAq4x584lo
http://www.youtube.com/watch?v=mdSThYaBgbU

Ooh, Lucario fighting Cherimu.  A short one, but it sheds a bit of light on
battling.  Note that the options are on the touchscreen - presumably, these
can be controlled with the stylus.  I suspect that moving your character,
therefore, will be a case of guiding them with the stylus or using the
buttons, just like Animal Crossing.

The second video shows an item being used.  Not wonderfully interesting, but
you get a glimpse of new Electric squirrel Pachirisu.

http://www.youtube.com/watch?v=EORYACvUa9Y

Choosing your starters!  Not dissimilar to choosing the RSE starters, and
indeed, not that interesting a video if you've already seen the new
starters.  But, y'know, for the sake of completion ...

http://www.youtube.com/watch?v=Am_bom4SzKE

A Japanese advert for the game.  Absolutely phenomenal.  Some 3D footage of
the new legendaries, as well as several snippets of new Pokémon (sigh, and
Pikachu) in battle, a shot of a Pachirisu being given a crown accessory in
preparation for a contest, clips of various locations - including a snowy
area - and a map of the new area!  Look out for the artsy way in which they
demonstrate the Wi-Fi connection, too.

Steffan