Speaking of efficiency, INTP's are very efficient as well. NT's, generally speaking, are very efficient. While reading through this thread, it was weird for me to imagine myself as the less efficient one in a relationship. I can't stand not being efficient, but I guess the INTP's efficiency is a bit different than what most people think of when they hear the word efficiency. For me personally, I require an unusual amount of rest and relaxation so that I can give my mind a break from things and really recharge my batteries. If I've had a day where I'm out and about and interacting with a lot of people, then I will come home and engage my Ti by reading or sometimes taking a cat nap. To most people that I know, they think this is laziness. To me, it's a necessity and it's very efficient, because if I don't take the time to do it, I'm going to be so worn out mentally that I won't be of any use to myself or anyone else. My sense of humor goes out the window, as does my patience. When we have our proper rest (INTP's), we can be really fun people.
But, when we are rested and ready to go (and determined), I believe we are extremely efficient in the way we go about doing things. I have had situations where I saw an ESTJ doing something that I thought was very inefficient. I could see various ways that they could have done things WAY MORE efficiently, but we're just not the best at expressing that verbally. When I've tried to express it, it doesn't always come out the way I thought it in my head. So, we may seem relatively inefficient at times, but I believe the way we see things in our heads (Ti) is about as efficient as it gets. ENTJ's are probably more efficient out in the public arena, but with our Ti, we are able to SEE, or spot, inefficiencies in people's actions/words immediately.
It would be really interesting to be in a relationship with a female NT. I've only known 3 and two of them were relatives (2 INTP's and 1 ENTP) - but have never met a female ENTJ.