Depends what your going for. Personally I would never get one but they're worth it if your going to use it. If scarcely put the rear seats down and put it in the car.
I would never do it for looks. Honestly, if I didn't use mine much, I would probably take it off when unneeded. I don't see any down side if you need one and keep it on, I think it looks worse than stock on most cars, as good as stock on the right car, and adds weight as well as it isn't free. Not a mod for myself.
Get if it your actually going to use it. The "look" is really played out, I have mine collecting dust since I only put it on when I use it. And well, I hardly ever do.
here is a picture of it after i sticker bombed the fairing.
that is true the look has been played out but i use my rack everyday, so you are going to use it a lot its a good investment, instead of getting back seats dirty, but its just for looks don't do it.