Buttoned or unbuttoned if wearing a shirt and no tie
Unbuttoned if wearing a vest or sweater as well
I have never liked the look or feel of a three-piece suit with the jacket buttoned.
I only have 2 button suits. Tend to wear it buttoned up on the way into and out of work (save for when on the Tube and stretching one arm horizontally/vertically to grab a railing).
When in the office (where not everyone wears a tie these days), it's off 90% of the time but when worn, I often have it deliberately unbuttoned as it seems ever slightly too stiff/formal in that setting when done up.