If I had known how well Diablo III handled multiplayer on the Switch, I would have bought it two months ago when it came out. I say that even having played the game to death on PC.
My house is a single Switch house. We're not really interested in buying a whole extra console to be able to play games together, so my wife and I are often hunting for good couch co-op games that we can play together.
Diablo III handles the mechanics of couch co-op better than any other Switch game I've tried. The Switch has an interesting system of multiple user profiles: each time you want to play a game, you choose which person you're playing as, and it keeps your save data separate from others. So my list of Diablo characters are on my profile, and my wife's are on her profile. Cool.
In my experience, those profiles are usually totally isolated, but not with Diablo! If I want to play with her, I can pick up a controller, hit A to join the game, and it will prompt me for which other profile I want to play as. When I pick my profile, it shows my list of characters and I can choose one. And now we're in the same game together, playing with the same characters we've been playing on our own separate profiles.
I admit I had hoped this was how it would work when we got the game, but I hadn't really expected it to be true. More Switch games that support co-op play should embrace this way of doing things. It made me so happy to have this kind of flexibility in how we play the game.