Not a huge fan of Gregtech honestly.
It's nice that he's added more stuff to IC2, but it's tied so much into a generally shitty design philosophy that it ends up being more of a hindrance than a benefit.
Here's what I mean. Gregtech has a very specific design plan for how people should progress and how long it should take to do stuff. It's terribly linear and depends on people following an extremely strict plan. Which a pain if you just want item X. Because then item X is locked in Tier 5, and you have to make items A, B, C, D, E, F, G, H, all in sequence to get it. And you can't just make one of each item either. They have to be automated so they can process a ton of resources. Which ends up meaning that if you are going to make Item X, it damn well better be worth the effort. It discourages experimentation and creativity.
Which is ok if Item X is a new item introduced by GregTech, or if GregTech was the only mod in the pack. It's no ok when Item X is an item from another mod, and you have to progress through a pointless techtree for that single item. Which often has a it's own proper place in progression that GregTech breaks.