Performance of a 27mm on an X-PRO1

I once had a 27mm on an X-E1, both with the latest firmware. No way to sugar coat it, the AF sucked. Slow, noisy and it hunted.

I'm thinking about putting a 27mm on my X-PRO1 as I still love the focal length.

Question: What was the performance like? Was the back button focus, when on MF, fast and accurate?