Main thing I used mine for was continuing to play a game when someone else wanted the TV; I could just switch to "display on controller" and keep going. Not such a big deal these days but back then it was pretty nice!

Asynchronous game design is something that holds a lot of promise. Traditionally, that was something reserved for online multiplayer in PC games. But suddenly it was possible to design local coop around one player interacting with the game in a different way than the others. The idea is still really cool, but I think most devs are unwilling to experiment with such a niche product.

The idea was to have two different screens displaying different information and there would be interactions between the two. Like the Nintendo DS's two screens. I played a tech demo(?) at the store where you'd aim a bow and arrow with the Gamepad at a target that was on the TV.

The idea didn't really end up panning out for most games.

Critically, it could stream something different than what the console was rendering to the TV. At the time it seemed Nintendo was hoping for the kind of design explosion the DS had early in its life, and a few titles trying such things were really good, but for many reasons it didn't stick the way the DS did.

Screens were slightly less ubiquitous then. You could continue playing on the controller when dad switched the living room TV to some sports.

> it kind of make the portability useless

It's not actually portable, it's purely a controller.