I'm a leftie, but I knit rightie. When I first started learning, I tried to learn leftie, but it was confusing because all the videos and stuff were geared towards right-handedness. So I learned right handed and now its natural...Slightly ambidextrous maybe?
If it makes any difference, I knit mostly English style.
Now, my little sister is a leftie and she knits leftie, just mirroring everything I do. She tried to learn right-handed and it confused her.
Each to their own, I suppose...