I'd like to opine some on the concepts of challenge, grind and balance as it relates to games and gaming, since these are terms that crop up a lot in this thread, and others that are about the balancing between mod's
First, there is the matter of balance. balance is not a single term for a single word, but is used interchangeably between different forms of balancing. balancing is all about making everything seem fair from a subjective point of view. with a big player base this becomes increasingly harder since balance is a subjective experience, and not an objectively measurable one.
for instance, it is common in gamer culture to want to beat some kind of challenge before being given a reward. (bee it a new shiny sword in wow, or a powerdrill in mc)
When talking about what level of work that is needed for a particular reward we are generally referring to the difficulty of the game. people have different opinions on what level of work should have to be performed in order to gain certain results. that is why we indeed do have difficulty settings in most games in the first place.
However. there is also grind. grind is the results of attempts at making something harder (read difficult) to do gone wrong.
grind is not equal to difficulty, and is something to avoid if possible. Common types of grind is to have to keep digging around after a resource you need to keep progressing in a game, or to keep having to do fetch quests in EVE online for a corp to gain access to some agent or other.
But grind is also a subjective measure, and peoples tolerances for doing repetitive tasks vary a lot. some people find the repetitive fetching in eve online to be fun, I personally prefer more action, but that is all about subjective taste in entertainment. ones person's grind is another mans entertainment. that is just how it is.
Mow Let's look at a couple of examples from gregtech. since we all are familiar with it.
In order to get the IC2 drill without gregtech, you need to first find some rubber trees and tap those. that requires walking around in the landscape while possibly being assaulted by baddies. (classic fetch quest)
Then you have to dig a hole in the ground til you find a certain combination of pretty common resources, then you smelt some ores, set up some special blocks, craft some more items used to craft other items, and voila. a new shiny toy is yours to play with.
This toy is one that makes all that digging around for resources more convenient.
Now let's compare it with gregtech. (the 1.4.2 version.. not the new one)
You start out the same as before. you go fetch some rubber, dig a hole in the ground and search up some resources for making a portal.
then you take this portal to this other place where the baddies are tougher and meaner than the ones you faced to get rubber, so that you can get this other harder to get resource you need so you can convert some of your previously mined resources into a tier 2 equivalent. then you go home and do the same thing you did before. you craft things that let you craft the things you need to craft the item you want, then you combine it all into the reward.
Comparing these 2 we see that a whole lot of steps got added, while the main quest stayed the same (getting a power drill). the number of sub-quests increased as well, with some quests being the same as before but with a different target item, while at least one of the quests was significantly harder to do due to the higher power of the baddies you have to fight to get the item you need.
On the plus side, you ended up doing some of the quests needed to gain access to other parts of the modpack. so none of the extra steps where actually solely good for getting the quest reward when looking at the pack as a whole. If you were going to do anything in railcraft for instance then you would have had to go on that nether trip regardless. the only difference is that you would have had all your toys before going on the trip. making the trip a lot easier, since you would have a lot stronger gear. (difficulty as in chance to not succeed, rather than as in actual physical effort, this kind of difficulty is described as demanding player skill as opposed to needing patience)
There is no character progression in minecraft, and the character only gains strenght trough his/her gear rather than leveling up like in wow, or by waiting around for skills to train like in eve online.
This leaves equipment as the only way to balance difficulty in minecraft. and doing so without creating any grind for someone is nearly impossible.
For someone who are gung ho about fighting ghasts with only their bare hands will find the nether trip boring. it becomes a game of chance, and not one of skill anymore. but hey. for those who don't spit fireballs back at ghasts the trip is maybe too hard to do at that point. and they will get frustrated when they find they have to kill x number of even harder to fight enemies like the blazes in order to get the item they need instead. or they end up having to default to searching for endless hours for those magma-cubes that only show up after you have found more than enough magma-cream. again it becomes a grind instead of an exciting adventure. both of these scenarios are expamples of what people like to call grind.
Gregtech is a mod that adjusts how and when a player has access to certain items that have a big impact on how difficult a task is perceived. this is either to your liking, or it is not. this is an entirely subjective thing, and we can probably all agree that we will probably never agree on any balance between effort needed to obtain these items and how we should be able to obtain them. this is what config files are for. gregtech allows you to adjust it to your preference. entirely removing the need for the nether before getting your toys is a choice you can make.
And no. as a "hardcore" player, I don't mind editing the configs, so if the FTB team decides that GT is too much then fine by me. I'l just add it myself and then tweak my configs to suit my style. I do hope they keep it in mind tho, and don't introduce incompatibility issues that are too hard to solve.