I have them on for two months and even if the road is wet, mud guards keep me safe from all the dirt and water on the ground. Wihout them, i got covered with filthy water drops all the way up to my neck.
That being said, they have a very DIY feel and looks to them. Rear ones are great, the front ones seem to be more of a mess. They hardly stay on their place, they start really low at the wheel which maskes them very exposed to anything you drive over (rock, curb...). I broke one when trying to get the board on a curb. It is 3D printetd, so it's fairly brittle.
Design wise, they look cool until you see the forn ones have to be zip-tied to stay in place; it works but needs constant tinkering to keep it straight.
I'd appreciate if they would have an easier attach-release system to put them on/off with no tools (now skate tools are needed).