So, GregTech: is it worth it?

I've heard a lot of people say that GT doesn't play nicely with a lot of mods, or causes incompatibility errors.
What I want to know is: is there a point to installing GT if I'm already going to have Reika's mods, Engineer's Toolbox, and the like enabled?
Does GT add anything that could potentially be more useful or endgame than what I already have available?
"Yes" or "No" will suffice.