I guess I am in the minority then when it comes to enjoying O'Brien. Personally, and its just my opinion, I couldn't stand him or his family. Whenever a O'Brien centric episode came on when I was doing my first run-thru of DS9 I would groan and suffer through it.
I found him to be a pompous and arrogant character. I didn't like that he said he was once a soldier (isn't he technically still a soldier in Starfleet) and if this was meant to be that he was in the infantry prior to being an engineer, well that should have been a bit clearer. He was also racist, referring to the Cardassians as "Cardies" and "Spoonheads". As a Soldier myself that has served in both Iraq and currently in Afghanistan I do not refer to the enemy by racist terms. Alot of Soldiers do I know, but if I hear it I correct them on the spot. O'Brien seemed to be given a pass for his behavior and that didn't sit well with me.
He also treated Bashir like an inferior when they first met simply because he was an officer that spoke alot and that annoyed O'Brien. That just didn't sit well with me, but I totally understand that it was the starting point of what would become a strong relationship between the two men.
I also do not care for Colm Meaney as an actor. I know everyone here loves him and like I said, I know I'm in the minority, but I have not enjoyed anything that I've seen him in. He isn't believable to me as a gangster or any other role I've seen him in.
But again, that's just me. It doesn't bother me in the slightest that other people enjoy O'Brien or Colm Meaney. We all have different tastes, likes and dislikes.