I didn't purchase them, but wanted to wait and see how dirty the car gets without them.
For the rear, I'd pass, the dirt only covers a small part of the rear bumper. However, I have noticed in the rain (and it rains here a lot) that I pretty much have to run the rear wiper all the time - not sure if rear splash guards would help. Anyone with them care to comment?
For the fronts, I can see those a bit more as the dirt tends to go up the front /rear doors at an angle, but its not really all that bad and confined to a limited area.
In both cases, I think the shape of the body and plastic wheel arches almost makes them not necessary. They're also kind of small so I'm not sure how effective they actually are.
I want to maximize my fuel economy so I didn't opt for them, and probably won't. Not a great need IMHO