It has a stylus. A recess in the upper left of the unit hides a small, white, roughly DS Lite-size stylus. Interacting with it brings up the familiar feeling of poking at a DS screen. Much like the handheld's bottom screen, the Wii U touchscreen doesn't respond perfectly to tracing with a finger. And multitouch is right out. Touching two spots caused the line I was drawing to jump to a point between them, much like the DS.
That suggests that Nintendo opted for a cheaper resistive touchscreen, instead of a capacitive touchscreen like the iPhone uses.