What are people even talking about in this thread? That you can play Xbox games on Switch? That Microsoft is taking over Nintendo online?

Come on.

I can't imagine it will be anything but apps and overlays.

Which sounds like it has the potential to be annoying, to be honest, especially if Microsoft convinces (or pays) developers to require Xbox Live for games. I'm sick of signing into things when I'm already signed into other things just so I can play a damn game. At the least it will be a hard prompt, though I'd very much hope it's just an option you can ignore.