He didn't really have a lot of screentime... in fact, he only appeared in 6 episodes (he was entirely absent from 2 and 3). But what limited screentime he had, I loved it. I enjoyed his complex psyche, how he carried himself as a benevolent hero, while hiding a crazy, megalomaniac nature underneath. I also loved that he was only true player of the game. Through his cunning and manipulations, he crippled Team Black and would've actually won the war if Ulf wasn't stupid.
I even liked his weakness to odors. Yeah, it's a weird character trait, but in the end this is a fantasy world. It needn't be as boring as irl. I think Ormund's weakness to odors is similar to the Boltons flaying people alive and wearing their skins: ASOIAF thrives when it embraces the absurdity and silliness of fantasy, rather than being all serious and dull like real life.
So I'm gonna miss Ormund. He was my MVP of season 3 and his absence from season 4 will be felt.