Yes for playing Wii games. I play it very often. At this point the only Wii U games I boot it for are going to be Xenoblade X and Fatal Frame 5 since 3D World is coming in 2 months (and I'm sure the other two will come to Switch too).
But I'll keep it to play Wii games since my Wii doesn't load discs anymore since a few years. Also so far Wii U is my only way to play the first Sin & Punishmen until N64 App eventually comes to Switch. So yeah, I use it a lot.
Wii games I regularly play on it are Sin & Punishment 2, Fatal Frame 2, Super Mario Galaxy 2, and Super Paper Mario. This month, I bought Tatsunoko vs Capcom, Nights, and Harvest Moon Magical Melody. I plan to replay The Last Story too.