Depends on the cat and the kind of eye contact. Slow blinks are great for calming an unsure cat and turning a relaxed cat into Jell-O. Assumpta is to the point where she often reacts to my facial expression and eyebrow movement (if she's paying attention).
Shy, timid, and fearful cats can be threatened by extended direct eye contact, and aggressive cats can take it as an invitation/challenge to escalate (not unlike people). I turn to the side and yawn a lot with scared and aggressive cats so that there's no mistaking that I'm not a threat. It's not a dominance thing as much as it's just threatening and icky to be stared at, KWIM? It's why cats always ignore the "cat people" in a roomful and go straight for the ONE person who's allergic...that's the person who's not staring at them, the one who is trying to be invisible to cats...and thus, the most nonthreatening person in the room.
I'll look Assumpta in the eye all day long, and it's just fine with her (she seems to enjoy kneading on my chest while gazing into my eyes and drooling on my face...but with cats I don't know and shelter cats, I don't do prolonged eye contact.