It doesn't interfere with the function of your struts so it really doesn't "harshen" the ride but it will "stiffin" the ride. You'll notice it. Only thing gonna really harshen the ride to a real noticeable degree are things like lower profile tires, stiffer springs, coil overs. even strut bars to a degree.
but I guess it depends on your idea of harsh ride.
Only real disadvantage is gonna be if you just don't like it. That and in the snow it is a set back. Makes the rear end a bit more prone to step out on you. But as long as you don't go getting like this beast of a bar I really don't think you are gonna unbalance your car,not like it, or have many problems in the snow.
Stay like....20-22 and you should be solid since our front bars are 20.