I spent a bit of time with the 3DS yesterday. The 3D in Pilotwings is extremely mediocre, and the sweet-spot for it to work felt too small with weird color shifts any time you wiggled your head even a little bit. I am very glad that the slider goes to "Off" for the 3D effect. The screen just feels like very "first gen" tech with the 3D turned on.
On the other hand, the screens both felt like much higher quality screens than the DSi. They are a tiny bit sharper, but they seem to handle black a hell of a lot better. By comparison, they felt closer to an iPhone 4 display with great blacks, than an iPhone 3GS screen with it's dark-blue blacks. That was just my initial impression though. I'll have to spend more time with it to confirm.
In rendering capability, it felt like a Wii. Better than a PSP, but not really getting close to a 360. I'd say it's pretty on-par with an iPhone 4 again with the images it can produce, sans resolution. I'll need more time with a variety of games to further judge this.
The body and the feel of the hardware isn't nearly as clunky as I thought it would be. I was fearing a return of the original DS, but this is closer to a DS Lite in execution.
So, the 3D is a flop of a gimmick, but the large processing improvement over the DS line still makes it worthwhile. The lack of a real resolution increase is a bit disappointing, but with proper 3D acceleration hardware now included sub-pixel rendering is now a possibility. This can bring a much sharper "feel" to the screen without more physical pixels.
Now to see if the lame 3D turns this device in to a Virtual Boy, or if the improved hardware just gives the large volume of classic DS devs more to work with in the "flat 3D" DS style of game.