I have two Fiestas with powershift transmission, a 2011 and a 2017. I had the transmission seal replaced and new clutch pack in the 2011 last December at 116k miles. I bought the 2017 in February, mainly because I got a great deal.
Before buying and after learning the 100,000 mile extended warranty no longer applied, I did some research. It is true that after the mid-cycle refresh the warranty return rates were much better, so I would at least avoid pre refresh models. This is the case for the Fiesta, I assume the same would hold true for Focus.
I don't know the extent of the changes after the refresh, but the new Fiesta tranny seems much improved. It is quieter, and has never gotten confused, especially during low speed driving maneuvers (I often kept the old one in L while in parking lots or stop and go traffic). That said, a DCT does have a different feel to it. I personally like it, especially after driving some rubber band CVT equipped cars. Others may disagree.
Also, I agree with fuzzymoomoo, check the service records. My worst experience with this transmission is the fact the service department has a hard time repairing these. It took two visits to and several weeks to get my 2011 right, and they charged me for a motor mount that probably was not faulty.
My 2 cents for what it's worth.