Plus, once you get mods that do damn near everything IC2 does outside UU-Matter and quantum armour (single mods, that is, I know you can do it with a mix), its entire purpose is whittled away in the face of the many hurdles you have to overcome in learning the complicated, over-punishing energy net. You know what does do complex energy right, in my opinion? RotaryCraft. You've got to pay attention to what you do, and there are consequences for fucking up with certain things, but the potential payout is enormous. The potential payout for IC2? Speedy smelting and little bonuses from their ore doubling mechanic. Before you bitch, I've played IC2-exp quite a bit, and its still irritating as hell to use, even though I know what I'm doing. The automated mining system is smart, but you can't give it enough power to both mine a respectable area and do so efficiently, and the miner itself can't handle fluids without a pump. Its a pain in the arse, and it is eclipsed by quarries, digital miners, RotaryCraft and Railcraft borers, hushers, and AE-based tunnel bores. The mechanics are annoying, they're not fun to play with, and the punishments do not befit the crimes you commit.
Again, if you want something hard, go RotaryCraft. If you want something simple that does almost everything IC2 does, but better and smarter (albeit a tad more expensively, in some cases), then use Mekanism. Or Engineer's Toolbox. Or Thermal Expansion. Or even freaking Thaumcraft. They are all far, far more interesting that IC2 and far less annoying.
Note that the above post is my opinion and is not to be taken as a presentation of facts. Anyone caught interpreting it as such will be kneecapped with a claw hammer.