I don't know Cillian O'Connor but I dislike the bloke purely from watching his actions on the field.
For example I recall him jumping around and banging the ground trying to get the ref's attention in the replay last year against the Dubs when he was barely touched.
He also has a head on him that you'd love to smack.
To me he epitomises the arsehole modern day player. Delights in being seen as an athlete and all that goes with it when in the end he has fuck all to back it up. I am sure he was one of the players who wanted rid of Connelly/Holmes because they didn't meet the level of perfection in coaching that the players demand - fuck off win an All Ireland before you can start making such 'demands'.
That said I think he is a good player. He rarely misses his frees and has gotten a few big scores for Mayo down the years including an equaliser in 2015 semi in Croker versus Dublin, He is nowhere near the level of Padraic Joyce though.