Yes I have a powerflow and I will say that it sounds actually nice. It's very quiet with a sports cat, too quiet actually. I run a decat for extra noise. It sounds nice on the blip but driving normally it's like driving a normal car with no drone whatsoever. I do 40 miles a day and I'm 32 so not a young chav anymore. For me it's nice and subtle with noise there if I want it.
I know many people will say that about the exhausts as they are hard to word but I will say, that exhaust need to be heard in person in and out the car. It's Wales hard to tell otherwise.
Build quality is not perfect. There's definitely a difference in quality over a premium brand but it's also cheaper. Mine is a 2.25" system also, which keeps the noise levels down.
I personally don't really like the look of mine but it sounds as i like it and so far it's not broke so itll stay for now.