Here's my two cents:
In my mind, ammochain isn't necessary in the standard game. On the harder difficulties(UV/N!), you don't have to worry about ammo generation that much, and you don't have the luxury of going for a certain rigid build, you need to have room for improvisation in your trait selection, i.e. you have to be able to adapt to the situation. On the easier difficulties, you don't have to think so much and the game is more forgiving. Think about the prerequisites for ammochain. They're pretty brutal, considering that they're all more or less geared towards a chainfire build, with no defensive traits along the way, I might add, and the only chainfire weapon available in the early game, the chaingun, is next to USELESS, because you can't hit shit with it without an accuracy buff of some sort, so you have to survive with a shotgun for the early game, even if you don't have the most suitable traits for it, and only upon hitting level 7 or 8 if you picked juggler, do you get rewarded for your hardships. And even then, accuracy is a problem, unless you find enough spare agility modpacks, so I think the unlimited ammo vs. accuracy is well balanced, and the main source of imbalance is instead the effect that ammochain has on your inventory management. Having ammochain frees up so much more space for spare medkits, modpacks, envirosuits, additional weapons, armor, you name it.
The other source of imbalance could be the traits that ammochain blocks (or doesn't block). Ironman is very powerful, and so is hellrunner, but having ammochain require reloader, as suggested in this thread, would be even more brutal than the current requirements, because getting ammochain would render reloader pretty much redundant.
I think the only times it makes a whole lot of sense to go for an ammochain build is when you're playing AoMC or Ao100. Why? Because on AoMC you don't have to worry about accuracy and on Ao100 the enemies are so tough and numerous as you progress that you're going to have great difficulties without a steady ammo supply, and the only times I've actually won Ao100 were when I found a sniper modpack and combined it with ammochain. I'm not sure if it tells more of my skill or the sheer power of the combination.
Additionally I've considered ammochain merely a milestone in individual development. My own player evolution has gone from a very shotgun-heavy playstyle through ammochain to a more experimenting, flexible trait selection, with emphasis on the early eagle eye.