I was ambivalent…it annoyed me in Pokémon Go as they Ditto disguises as the most common Pokémon (meaning you use up all your Poké Balls looking for it, not ideal when you live in a rural area), whilst Zorua kept appearing as Feebas, which I really need for a quest!
But when I locked onto a Grafaiai and its name said 'Zorua' as it legged it away, my face lit up. I really like it. There are problems with the OW Pokémon - like how if you exit a battle at the wrong moment a wild Pokémon will instantly trigger another encounter, and at least twice I got stuck in a cave because I couldn't walk around them - but this isn't one. As Serenity says, it makes them feel more real.
I'd love it if they took the anime canon and made all the Ditto ones have the Ditto eyes in their sprites, but given they can't even design a half-decent PC Storage this gen I know that's never going to happen (seriously, I can't jump between boxes holding a Pokémon any more - what is this, Gen III?)