You know, after a while you just have to learn to ignore the people whining about things being OP. I'd much rather something be fun, than worry about some mythical 'balance' which is different from person to person and is altered drastically by every mod. When it comes to balancing mods, you have to go at them with one of two mindsets: Balance vs. Vanilla, or Balance vs. Specific Mod.
Balance vs. Vanilla, only works if it's the only mod installed. Buildcraft is balanced vs. Vanilla, and it does it's job. It automates furnaces, and mining. (And construction, but that's split into two things covered by the those two, time and tedium.) And alone in vanilla, it's perfectly fine. It does it's job exactly as intended without any problems. Once you add another mod, such as TE, or ABO, the balance changes and it's arguably stronger than the basic mod, because now you can smelt and carry the power around. There's no longer a need to make space and set up engines and the support network on site, so now you can go anywhere with a tesseract, a redstone energy cell and a quarry and set up a mine instantly. Plunk, plunk, plunk, and the quarry takes off, mining along with no more interaction. Is it still balanced? Maybe, maybe not.
Balance vs. Specific Mod however, assumes you have the mod it's balanced against. For example, Gravisuite. It introduced the Advanced Electric Jetpack as a stepping stone between the Jetpack and the Gravitation Suit. It is predicated you having and using the ore doubling capabilities of IC2 to get the resources necessary to build it. But what if you want it and don't want to build the IC2 infrastructure? Guess what? You don't need it. For all the reliance on IC2, you need only a few items from it. Forget building all that power, you can just build an MFSU, skipping the whole chain, and plug it into a Railcraft Steam Turbine. It charges the MFSU, and then throttles down and all the steam goes into Industrial Steam Engines. You need IC2 only to ensure the game doesn't crash and to build a single MFSU to charge your AEJ. No other infrastructure is necessary. (Yes, you need the IC2 components added, but since they're only built in the quantities necessary to construct the AEJ, you're not keeping them around.) If all you're doing is getting an AEJ, is that overpowered for an otherwise vanilla universe? Absolutely. Is it frustratingly expensive using only vanilla furnace smelting? Definitely. Does the prescence or lack of a mod affect balance? Absolutely.
So before you scream: This is OP!!! Look for the balance. Is it Vanilla or Mod balanced? If it's vanilla balanced, play with just vanilla and the mod. If it's mod balanced, play with just it and the mod it's balanced against. And stop telling the rest of us what we should think please. We're capable of making our own decisions.