The first details about Spiderman 3 for the DS are starting to come in via an interview that IGN conducted with Vicarious Visions.  VV has been responsible for many successful games on handheld systems including the Tony Hawk franchise.  They also are planning big things with the DS version of the game, especially graphic-wise:

IGN DS: How did you manage to create a massive streaming world on DS? That sounds amazing.

Christopher Olson: We have a long history of putting a tremendous amount of effort into developing our handheld tools and technology. We’ve developed our DS technology to the point that we are able to stream textures and geometry straight into memory allowing us to create much larger and more detailed worlds. For Spider-man 3 DS we melded our technology with an interlocking city neighborhood design that allows players to freely traverse through the massive city environment.

Sounds awesome that they were able to do this on the DS!  This could open lots of opportunities for other games on the DS in the future.

Source: IGN DS