My sith warrior's female and I married Quinn just before Voss. I remembered thinking when I left Voss that Quinn better not be the one to betray me because he was my best geared companion. Sure enough.
Luckily, the fight isn't hard solo. When he betrayed me, my warrior was confused and asked him if he was breaking up with me.
After kicking his rear, I force choked him (which did result in a loss of affection if I recall but it was really small) and then forgave him. I told him we'd keep it between us and not tell the others, and then told him he'd be making it up to me in the bedroom.
Waiting to see how that pans out in the future. I can see another betrayal coming later down the road, the player automatically blames Quinn because he did it before resulting in the rest of the companions finding out about it (if they didn't know), and then you find out it was someone else.
I did the warrior's story line back in December so a bit fuzzy on some of the details like affection lost, etc. But I do believe I lost some for force choking him only to gain it back when I told him I wouldn't tell the others. When it doubt, check out torhead.