Now I've gotten to HV tier and have built an IC2 mining laser (though I haven't built HV machines beyond what I needed for that yet), I don't mind the redstone centrifuging so much or wading through NEI to try to find the fastest or most material-efficient way to craft different items, but I've come across some oddities I'd like to mention:
GregTech internal logic issues (maybe somebody can explain these, but at the moment, I don't see the logic behind these details):
1. It takes 10 times as much time and EU to smelt steel dust in an EBF compared to smelting wrought iron to get steel (setting aside the time it takes to prepare the wrought iron and oxygen)
2. It takes almost twice as long and more than twice as much EU to smelt one pile of aluminium dust in an EBF than to smelt three [green] sapphires or three rubies (which will provide enough nuggets for one ingot).
3. With my current set of mods, I can use an MV-tier fluid extractor to get liquid aluminium from 101 different items, and liquid steel from 239 different items, including ingots and plates, but not from the simple dusts (unless I turn off the blast furnace requirements in the config, which also allows me to smelt the dusts in a simple furnace as well, which I'm not certain is appropriate).
Wiki issue:
On the FTB Wiki GregTech 5 Mining and Processing page, near the bottom, it says:
I have to disagree. Even after making plenty of other electric machines, the forge hammer is still useful for the following:
1. Converting crushed ores to impure dusts (faster and lower EU cost than re-macerating the crushed ores)
2. Converting purified ores to purified dusts
3. Getting gems from gem ores (faster and lower EU cost than smelting the ore block, though I think it produces fewer gems per ore block than processing ore blocks to dusts and then autoclaving or implosion-compressing the dusts)
Inter-mod oddities (I presume some of these can be fixed via MineTweaker and/or ModTweaker, but it might be good if someone could edit the FTB wiki page on GregTech mod compatibility to mention them; I hesitate to do so myself):
1. In surface craters from AE2 meteorites, I sometimes find blocks that show as "gt.blockores.0.name" in Waila, and when I mine one, it drops vanilla iron ore. I've had vanilla ore generation disabled in the gregtech configs since the world was created.
2. Many Railcraft devices are apparently not craftable by default when GregTech 5 is installed: the steam oven, the engraving bench, the rock crusher, the feed station, steel tank valves/gauges (though strangely steel tank walls are still craftable), the boiler fireboxes, the void chest, and the metals chest.
3. Buildcraft and Forestry have their own recipes for a few types of gears, which in the early game are cheaper to craft than the GregTech equivalents, and no options in their configs for disabling those recipes.