As mentioned, IC2 is now pretty near obsolete due to other mods building ontop of the foundation of Buildcraft.
Personally, when I started with mods, I thought Buildcraft would be more obsolete, as it's power systems was terrible (designed on purpose that way), but with TE, we now have storage and more efficient transport systems.
In my current playthrough, I think my IC2 usage will be restricted to using Recyclers, and perhaps a Mass Fabricator. Everything else powered/controlled by other mods.
I believe that IC2 needs a shakeup or some brave souls to make addons that give IC2 versions of items available in other mods. GregTech is doing this in it's own way, but I'm not keen on it. The design process feels haphazard and no real clear development goal. I can understand the idea of end game tier technology and trying to address inconsistancies/exploits between mods, just the approach seems wrong to me with loads of new ores, some strange recipe ideas, waiting times, new tech items, etc.
Trouble is, all the mods are in effect in an arms race, all trying to outdo each other, so any attempt at a consistent balance between mods is out of the window.