I honestly don't think I would have bought one if 3D hadn't been one of the features. That probably puts me in the minority.
Without it, it's a little too similar to the DSi, improved specs aside. "It has an analog slider disc" isn't much of a marketing bullet point.
However, Nintendo has been good about adding new features and services that maybe should have been available at or closer to launch to distinguish it as a more connected device relative to the DSi.
From a cost perspective, having the 3D display added little to the overall cost of production; no penalty there.
From a performance perspective, shutting the slider off can be coded to enable faster frame rates should the individual developer wish to do so; again no real penalty.







