I'm glad I knew about the Quinncident before starting to play my Sith Warrior. Taking her relationship with Malavi very very slowly. She is about to reach Voss and they have just started flirting pretty much. This way the major build-up for romance occurs after she has forgiven him for that thing. Works better for me that way.
This is exactly what I did too. After trying for months to avoid spoilers, I finally gave in and read the huge Quinn thread that was around at the time. I think what makes Quinn's betrayal so darn awful is that so many people had gotten to the love and marriage stage of his quests. It became more like a double-betrayal.
By the time I got to the betrayal, I think I had somewhere around 6000 affection with him, and about 8000 with Pierce. It felt like my warrior and Quinn were at the "I'm beginning to lust after you" stage, with no major feelings involved yet. In the beginning I saw my warrior as a bit more power-drunk and reckless, and Pierce suited her. But after a while, Quinn's patient planning and meticulousness started to feel more practical than Pierce's "lets throw it all up in the air and see where it lands" style, especially when the doo started hitting the fan with Baras. The betrayal hit and my warrior's eyes were opened to now seeing Quinn as a real contender in the game and someone who she should take more seriously (rather than the teasing that she was doing up until that point.) The betrayal became a sort of springboard for the two of them to start actually getting to know each other.