There are plenty around. I'm sure most of them work similarly. One issue I had was my firewall getting hot on long trips. Did the louver solve that? Nope...
Another issue I was having was in the super hot California summers, the A/C would not run as well as I'd like it during stop and go traffic. Did it solve that?
Fuck yes it did.
I don't rock crawl as much as I did in my youth so I don't know what problems it was supposed to solve in that regard. Actually, come to think about it, I don't know what other problems people think it would solve or if they are imaginary. Ask me if I care.
As for water. I've been through big storms in California, Arizona, Texas, and New Mexico with my Poison Spyder louvers. Haven't noticed any problems. Water does get in when I'm blasting it during wash day. Again...ask me if I care. I'm pretty sure the Jeep doesn't care either.
Poison Spyder wasn't my first choice. I really liked the Gen-Right early models like the kind on Stu's site.
BTW, that Amazon model is an exact ripoff of the Poison Spyder hood louver. Don't know if the material is the same gauge or type, though. Gen-right ripped off their design on their newer models for the most part as well. But seriously, a real Poison Spyder hood louver is about $20 more than that Amazon ECOTRIC knock-off. Why would you cut corners? (pun)