I only consider something "overpowered" if it completely outclasses everything else in every way. In the context of multiple mods, and especially within each individual mod, I don't like it when I'm forced to go down one route because it's the most efficient (EE2, GregTech, etc). I don't care if it's incredibly difficult to go down a path, I just care when one mod is so much better at doing everything that there is practically zero reason to even consider doing anything else.
Exponential growth is not bad. In fact, it's a basic design that a lot of games follow. The problem is when that growth is 100% self-contained like EE2 (use collectors to make collectors), incredibly fast with minimal setup (block of diamond is minimal in this context), and generally requires relatively little time and effort (pull the collector out of a condenser). UUM takes an incredible amount of time and work to get to, and even then there are a few resources that it still can't get you.
Exponential growth is not bad. In fact, it's a basic design that a lot of games follow. The problem is when that growth is 100% self-contained like EE2 (use collectors to make collectors), incredibly fast with minimal setup (block of diamond is minimal in this context), and generally requires relatively little time and effort (pull the collector out of a condenser). UUM takes an incredible amount of time and work to get to, and even then there are a few resources that it still can't get you.