Berto, all I can tell you is that I've been around trucks for decades, and I've owned a dozen or so. I use all mine like trucks - hauling loads, pulling trailers, going places no self-respecting car weenie would attempt to go. I've been stuck a few times, I've been close to being stuck a bunch of times, and I've torn up and fixed trucks in the woods and on the side of the road enough to know what is and isn't worthless.
This vent mod addresses two primary flaws in the factory vent system. First, that vent is mounted on the axle. That's too low, in my opinion. The front diff vent is terminated up on the firewall, I believe, or perhaps the inner fender, but well above the axle housing. There's a good reason to move the vent up above the axle housing: Water. So this mod provides you with some added insurance that water intrusion will not be an issue for your rear diff. On old 4x4 trucks, this is one of the first mods we did to bone stock trucks. Back in the day, we would run a line from the rear diff and the front diff, up to a metal T-fitting on the firewall, and then attach a valve cover breather to that. With the T, it's easier to just vent the rear diff up into the taillight housing, with a fuel filter to act as a dust/bug barrier.
Second, this vent mod eliminates the very real, often experienced, closure of the factory vent from oil residue, dust, and crud, which plugs up the little covered valve in the factory vent. What generally happens is that the valve becomes essentially clogged, but when pressure builds inside the diff, it pushes the air out through the clog. The bad news is, when the diff cools back down and pressure drops, the valve's natural position won't allow air to be sucked through the crud, so you end up with negative pressure inside the housing, which then pulls on the seals and contributes to premature failure. I'm pretty sure not all the seal failures are from the vent sticking, but it's a contributing factor in enough of them that a cheap mod which eliminates that possibility is worth doing. The guys bellyaching about it being "worthless" don't understand enough of physics in the real world (based on my discussions with them on this board) to understand why the factory vent doesn't function flawlessly all the time. In a perfect world, like a clean room, that factory vent would function perfectly all the time. But in reality, it gets dust, gunk, grime, and crud on it, and it clogs.
I highly recommend this mod. You can do it one of two ways. You can source the parts yourself - using the Nissan threaded hose barb which fits perfectly, some fuel line, zip ties, and a fuel filter without a check valve (total cost ~$20-25) - or you can buy the pre-packaged kit from Cajun and just install it (total cost ~$40). It's up to you how you proceed, but I highly recommend this mod. It's easy, carries no risk of harm except to your knuckles during the install, and provides a couple of good benefits you don't get with the factory vent.