I have to say, the first gang war book should have been in the main box. The 3d rules, campaign and expanded gang lists for the two included factions not actually in the main game as advanced rules? Very odd indeed.
I did think hard about it, but in the end I've said no. I really don't think it would have been played enough in my group to justify the cost. A terrible shame as I'm a big necromunda fan.
I did get a couple of escher boxes to add to my guard army, and the barricades and objectives box for scatter terrain. I also got an escher dice set as escher is my main gang (and guard force).