So far, my impressions of the DS have been the exact opposite of Dan's. The absolute aiming in Metroid Prime is but one of the aiming modes - the standard pen look method is still there. Screen looks to be VERY durable - it's not suggested against using your finger to touch the screen, though I wonder how accurate you can get.
Mario 64 DS has a couple of cool things to play with - instead of transforming Mario's face, it morphs into pen wireframe, and you can drag that around. 30 new stars (about 6 new levels?) and a bunch of minigames, plus the entire original make that a worthy buy.
They even had left handed mode for Metroid Prime!
WiFi is pretty cool, though I haven't been able to try it out myself. The local EBGames has 2 DS set up to multiplay Metroid Prime, though my friend who had bought it was able to join up in a 4 player multiplayer game from a decent distance away (10-30 meters they claim)
One VERY interesting bit is that if you run Netstumbler with the DS on/in Pictochat, the DS shows up!
In but one generation of software, Nintendo has already eclipsed what PocketPC developers have done with the touchscreen in 5-6 years.
holy internets batman.