Opinions on what is a "safe speed" vary quite a bit, as this thread illustrates.
I've lived in the Top End for over 30 years, and have driven the entire length of the Stuart Highway quite a few times.
Since I retired five years ago, I usually make two trips south per year.
In December 2013, I left Darwin on the first day of school holidays. I was expecting plenty of traffic, but it was very light.
I set my cruise control at 110 kph. That is for reasons of economy - I have found that at 130, I use a lot more fuel than at 110 kph.
As best I recall, I only got overtaken less than a handful of times in the 2,500 km to Port Augusta. I only overtook two or three trucks and a couple of buses.
Not much coming the other way, either. As I say - traffic was surprisingly light.
A few observations for those who haven't been here -
from Larrimah to Katherine, there are numerous Agile Wallabies. They are small, even for a wallaby, but their fur is great camouflage. You don't see them in the daytime; they are a bit active at night; but they are at their busiest at dawn and dusk. But they are suicidal: they stand by the roadside, and at the last possible moment, they leap in front of you, rather than the more obvious choice of leaping away. I try to avoid that 180 km stretch at those times. On that trip, my son counted 198 deceased wallabies on the road or the verge, in 180 km.
The Stuart Highway doesn't have many bends, nor many hills. It is at sea level at both ends, rising to 550m above sea level at Alice Springs (the highest point is a little further north).
So, it's not challenging or exciting driving. Wandering livestock is, in my opinion, the greatest danger - either that, or fatigue.
So the 130 km limit doesn't much affect me; nor does the 200 km of no-limit. And I can't imagine myself changing my habits on my next trip.