Interestingly enough the 2013 Focus I had (leased) for 3 years and about 56K km did not exhibit any major problems much less shifting to neutral on its own while driving.
Yes, the transmission made some funny noises sometimes at low speed stop&go (from the clutches engaging I would guess) and in 2 occasions I think I got an warning that transmission is overheating and to pull over for 8 min (I remember I was thinking that is a very specific number) to let it cool down. The latter happened when I was crawling on a steep ramp for 30-40 min to get out of a busy underground parking after an event. The warning came on right when I hit the street so I ignored it and kept driving.
And yes, in very specific driving conditions it was slow shifting but that only happened with aggressive driving not normal driving.
I guess I was lucky or didn't have the car long enough to face these problems but I too felt it's not a tranny that I would like to have long term.
Otherwise the car was reliable for the time I had it and it was nice to drive for a regular car. I only had one problem with the driver door handle which was replaced under warranty (the proximity sensor stopped working).