I've got one, loving it so far. It's a '17 model currently with 7600 miles on the odo. I daily drive it. No problems with it yet.
I have driven just about every car that competes with the ST and the Focus in general before I purchased the car. This includes the Fiesta ST, Golf GTI, WRX and STI, Civic Si, regular Civic, Mazda 3, MazdaSpeed3, regular Focus and Fiesta, etc. and I liked the Focus ST best so I bought one.
Compared to something like a regular Focus or Mazda 3, the ride is stiffer and the fuel economy isn't as good, but it is much faster and better handling.
Compared to the Civic Si and VW GTI, it feels more exciting/performance oriented to drive and is way faster than the two. Compared to the WRX, it is not quite as stiff and uncomfortable as the WRX, and being fwd while the WRX is awd; it is slower off the line because it just wants to spin the tires.
I drive pretty sane most of the time and average 26-28 mpg on my commute (including traffic), which I am more than happy with. The interior design and materials and fit and finish is very good for the price point aand the fact is is based off a compact economy car. It feels very quick and the handling is phenomenal for what it is. I have the regular cloth seats, which are pretty comfortable and not nearly as tight as the Recaros. Interior space is good, the rear hatch cargo area is decent size.
Overall very happy with the car, and if you need a practical, (somewhat) economical car to daily drive, but really want a performance car and have only a modest budget, it's really hard to go wrong with the ST. For the price point, I am very satisfied and I have no regrets so far.
I have heard that if you purchase used, to avoid the 2013 models. It's the first year of the ST in the US, and generally early models of cars tend to have more issues than later production models. There are some issues they had at first where they had to issue recalls to fix and some bugs and design flaws that they ended up getting worked out later on. The facelifted (2015+ models) have some nice updates over the 2013-14 models as well. Chassis improvements for better handling, updated interior (nicer/more options, especially on the base ST1 package), lock/unlock button moved from the center to the doors, all 4 windows fully auto, better lights (IMO), among other things.