Yeah subframe/diff risers are definitely not needed unless you are extremely low, and the car doesn't function properly at all. I hate that I need to spend all this extra money just to keep it reliable at such a low height.
My car doesn't react properly, the height makes it harder to drive, its putting excessive stress on the axles, the tires rubs immensely everywhere up front, higher chance of damage underneath, and honestly I don't recommend it unless you are absolutely all about this look and style.
It is purely stylistic but it just looks too damn cool to me!