It's a normal auto, not a DSG(like in the gti), therefore you would almost never use it as the delay between pulling the paddle and anything happening is too long.
I have an old hyundai with the + and - down by the shifter. I've used it maybe a dozen times int he 10 years the car has been int he family. I also have these things in my FIT. I only use them before cornering or stopping, but that's cause I have a habit of downshifting in the wrx. If the paddles weren't there, I wouldn't downshift at all. So it isn't making anything easier or more convenient or safer. It is a feature added on for a sporty feel that is not provided. In my opinion, it is a huge gimmick.
Like I said, not a DSG type box that is rather instant. This is just a crap auto with a gimmicky paddle shift system so that people who don't know better, think this is the same as a gti/audi/gt-r box.
It seems to be working quite well for them