The Gamerpad screen only showed player hints while playing the E3 demo. No map.
That might be something specific to the E3 build, though, where time is short, eyes are all on the main display, and button mappings need to be clear at a glance to someone with no manual and zero experience with the game. I can't imagine we're in for a DKCTF scenario where in the final product there's nothing on the GamePad at all. I expect we'll end up with something like WWHD.
What we can be reasonably assured of is that we won't have any GamePad-dependent items or player actions like how TP (Wii) and SS relied on features specific to the Wiimote. And that's fine. I like the GamePad quite a bit, but like every oddball Nintendo interface, I don't see why people expect that it has to do either everything or nothing in every game to have a purpose at all. Its purpose is versatility, and suitability to a whole range of functions that are critical to some titles and completely optional in others. What players dislike, I think, is when it feels "forced"—when it's required for a function for which there isn't a good mechanical reason for it to be required, like the second-screen interiors in W101. That's flatly not the case with second-screen interface enhancements like maps and inventory, which are the very definition of things that are very nice to have but not required—which is why an implementation like WWHD's was such a perfect compromise, whether you loved the GamePad or hated it.