I haven't gotten into pneumaticraft yet, but watching a mod spotlight I see EVERYTHING uses iron. Jadedcat tweaked some of the recipes in AgSkies because of the high iron usage and allowed us to make some common items with ingots other than iron (i.e. hoppers and servos come to mind). My last playthrough on 1.0.5 had me constantly wishing I had more iron, while I left stacks of other metals sitting in my chests.
Does this imbalance still exist between iron ratios received from Ex Nihilo vs iron ratios required for building stuff? I might be a little premature in saying there's a problem, but I have concerns after looking over default recipes for pneumaticraft.
Autonomous Activators are very cheap to make and can pulverize cobble into gravel with hammers in their inventories; I fill mine with lead hammers since they have great durability and I hardly use lead. There is the issue of EntityScent being spammed because of it, and I had to disable Zombie Awareness until a solution is found. Just two (or rather four, with half placing) can outpace a sifter with 4 Autonomous Activators. It's very easy to get iron after that point.