So far I only own Splatoon 2 and Mario Odyssey.
Gyro aiming in Splatoon 2 feels awesome; fast, smooth, and responsive, far more so than analogue alone.
Odyssey... well, they're okay. Don't really add much, but flicking the joycon to throw the hat is kinda fun I guess.
I reckon there's a ton of untapped potential with motion controls on Switch; I thoroughly enjoyed their implementation in Wii games like Metroid Prime 3 and Red Steel 2, and now that both hands essentially have better-than-Wii movement detection, we could see some truly awesome motion-augmented experiences.