I'm an ESFP, and I have know many INFPs ESTPs and INTPs.
INFPs are my semi-duals.
INTPs are my duals.
ESTPs....yuck for me, but I know INFPs would love 'em.
I have first hand experience, that Duality definitely works! better than any other type-relation (Activity is not bad either)
I have dated all kinds of people (I AM an ESFP, after-all)
and I have found that the best match for me, (through EXPERIENCE), is my dual, the INTP.
and by the way, this not only includes intimate relationships, but ALSO friendships, work-related-friendships AS WELL!
my favorite types in the world, (out of my first-hand-experience) is my Duals! those funny INTP bastards. and sexy INTP cuties.
therefore, my conclusion (based on my first-hand-real-world-experience), is that Duality can work 90% of the time! and work better than all other relation types!
Hurray for Duality! that is the saving grace of life.