The upcoming Nintendo 3DS worries me because of the 3D aspect. Not the technology--I'm sure that works--but for the potential difficulty I could have with my eyes. It's a crap shoot whether or not I'll actually get anything out of the 3D in a film. Even with something like Avatar, there were long stretches of the film where I couldn't see anything special. The graphics were nice, but it wasn't popping out (or stretching back) for me.
Seeing the above embedded video from G4TV helps me feel a little better. The explanation of depth level lets me know that I can adjust the screen to what my eyes can handle.
There are other nifty features, as well. The analog stick isn't a replacement for a D-Pad (I love a D-Pad like you wouldn't believe), but a precision tool. You aren't going to play a whole game making minute adjustments (unless that's somehow the point of the game, which more power to the developer who makes the metal detecting game for the 3DS), but you might be able to line up the perfect jump in a action/platformer.
There are some interesting location-based features as well. Essentially, the 3DS can tap into GPS features like a smart phone and interact with other gamers. It's yet to be seen how this will play out, but the connectivity element will surely draw in some reluctant gamers who can't get enough of the FourSquare.
I know for a fact I won't be getting this as launch (too many computer repairs and replacements to pay for), but I'm more excited for the system based off that basic overview of how the 3DS works.