Yes, it's available early and yes, early flight does break a lot of things. On the other hand, with twenty minutes work and a lucky world generation IE a witch dropping glowstone, I can have IC2 flight that is limitless unless I'm in the nether. (Solar helmet and basic jetpack). As opposed to something I have to produce fuel for, and land to refuel it, even if it does hold a frankly absurd amount. I'd definitely slice that way down if I were to be balancing a mod pack.
Part of me wants to wave the Rotarycraft flag and point out it can do 5x production, but another part is reminding me it can, but only if you have a LOT of iron already for the steam engines and it's not automatic.
I agree and disagree about the Nether requirement for steel. I like the idea, but then I put iron and coal coke in the blast furnace and then have time to read a fair piece of a book per ingot. I'd personally split the difference and tweak the Metallurgic Infuser recipe to require Blast Bricks in it's recipe. Gotta have the nether for steel, but you're not sitting there waiting on steel in the Blast Furnace. (Admittedly the IE one is much quicker than the Railcraft one.) But once you get enough steel for the Improved Blast furnace, you can start making blocks of steel instead of individual ones. Maybe even tweak the Infuser to require Coal Coke instead of just plain Coal.
Gating behind steel works when done well. Future's Edge seems to have the right balance. Yes, you need a lot of steel, but he didn't shove it so far back as to be unreachable.