The 2006 model had a couple of issues with the rear axle, but I believe the 2007 and onwards had no issues there. There was a recall that might affect the 2007 model (it got mine) regarding the bonnet catch being able to break and release the bonnet at speed on a rough road.
Other than that, there MIGHT be a DPF in the 2007 that would be worth talking to ChipIt about, ask for Robert and tell him you want a "DPF Delete Pipe" - that is, if the 2007 had a DPF (I don't know if it did, but if so, it's no big deal).
You should end up with a ute that has sufficient power and reliability for touring, nearly 1 tonne of carrying capacity (but take care there, the rear springs are a little under-rated for heavy loads).
The D40 is comfy on long hauls - reasonable quiet in the cabin too.
The D22 drivers here will tell you that the D40 isn't as capable off-road as theirs, then you'll have some D40 drivers say that the D22 resembles something lesser than the Model T and if I were you, I'd ignore all of that and treat it as playful banter.
The fact is that neither the D22 or D40 are terrible at off-roading, but both need some changes to do the harder stuff. They'll never be Baja bugs, but for getting out and away they're both equally good vehicles. The D40 has more creature comforts, smoother ride and more power, so if you're going to travel or tow, the D40 is the one to choose.
How do they rate against other utes? The Navara has a towing capacity equal to the Ford Ranger, Isuzu D-Max and Holden Colorado, all of which are superior to the Mishitbus Triton, Holden Rodeo, Ford Courier, Great Wall and Toyota Hilux. The Navara has more power and creature comforts than the competitors (of the same vintage). The Mishitbus does have a better ANCAP (crash testing) rating but I believe that's because of side air bags in the 2009 and later models.
If you're after a ute, the D40 is probably the pick of the bunch.
Service costs might give you a jolt - every 40,000km it'll cost near a grand, and the others are $200-$400 inbetween (every 10,000km). You can shop around though, just make sure that oil gets changed regularly and the coolant hasn't died, because your turbocharger depends on both. Oh, maybe invest in an EGT gauge too ... no matter the choice in vehicle.
If you're after a 4WD - you'll find that the Nissan range is not shabby at all, and it really comes down to how much money you can throw at the vehicle and driver ability.
It depends on what you want to get out of it. We bought our D40 Dual Cab STX brand new, and haven't regretted any of it.
