I've been making a Let's play for the past weeks (currently closing to episode 30, when I will switch to MC1.4.7), and I must say that there is a simple reason for not using GT in DW20's let's play: Too much things to do, in too little time (and I am not talking about mining, but about crafting!). You have to do a bunch of things in one hand, a bunch on another, and tons of stuff to do per mod. Also, the config options plays against the mod: it is hard to explain how to play with a mod for a mod when your settings might be different from somebody else's.
Personally, I found a bunch of failures on Gregtech's planning:
- Lava Generators: access the Nether (buckets, patience, lava, water, and a "cast" gets you the portal) and use a Nether chest, Mystcraft's portal (with Railcraft's liquid loader/unloader) or one of the new Thermal Expansion's "teleporting pipes" to move lava from there to your base. Storage it into a Railcraft tank. Lava generators (IC2) are cheap and more efficient than water/wind ones.
- Advanced solar panels: if you have this, the cost of making a solar panel with the default GT recipe acts as a bottleneck only, the tier 2 solars are 8 times as powerful as a single one... and cheaper.
- Other solar mods: having Redpower 2 means you have a cheap way (iron + blue doped wafers) to get solar power (or wind power!) and it now has a MJ generator. So you "need" IC2 EUs only for compressors, extractors, and few more things (more advanced, granted).
- Multiblock structures: While I love them, having to run the cables to the actual machine block rather than any part of the multiblock can be a pain, not to mention very ugly when you have to deal with differently layered machines (let's say the industrial furnace and the implossion compressor...). Being able to place the finishing block, at least, on any side of the machine would be better.
On a personal note, I tend to prefer small numbers without extra "0" rather than big thousands. I mean, I played World of Warcraft for years, and the difference between me with lv 60 and me with lv 80 was the numbers healed, not the ratio between cost and effect.
However, I find the mod more than interesting, specially since I tend to hate devoting more than half an hour or so per gaming session to mine (some mining is fine, ducting tape to my mouse's left button is... farming. I got tired of farming years ago).