I have to say I was totally shocked when Cullen basically took you on his desk. To me that is very un-Cullen like and my jaw dropped. Bull's romance is definitely and omg I can't believe I just saw that. I have to give the Bioware props for the romance scenes. They went in a good direction with them I think. At least there was no small clothes involved.
When does that happen? After the quest with Samson?
That DOES seem un-Cullen, but I also think that Cullen has always been holding back, especially if there was a female mage Warden. He's always followed the rules and whatnot, and it gets tiresome. He spent five years training to be a templar, and when he was a templar his entire life was the Chantry. Everyone he knew died in the Circle, and he didn't particularly care for anyone in Kirkwall.
Cullen is a templar, the Knight-Captain, he's commander of the Inquisition's troops. He always has to act tough and like a leader, even if he is doubtful or scared. Then he slowly comes out of his shell, showing that side to someone who he ends up caring for. She likes him back, and that must mean a lot to him. He's not scared any more, and that happiness ends up coming out in what seems to be a very un-Cullen fashion.
Yes, I read into things way too much. XD