Responding to the OP, this is why I think packs like Unleashed are killing modded minecraft. You say three prongs, resource gathering, building, and survival. Well, without GT in Unleashed, there really isn't much of a need to gather resources because there are only a few blocks/machines you really need, and they are cheap to make. Survival is a joke once you can make Nano, which again is cheap to make without GT. Beyond that, you're virtually invincible. You don't need quarries, you can mine out the same space in just a little longer than a quarry would take using a TC hammer and without all the supporting infrastructure.
Some of the more interesting parts of the game are tedious and require a lot of patience, which most folks don't have (including myself), so things like Bees, Crops, Trees, Thaum, Ars all get ignored for the most part unless you are magically-inclined.
Some of the mods appear to be in a race to see who can make things the easiest to do things... Steve's Carts used to be something used by a lot of people for tree farms and such, or even villager things and other creative things. Why bother when you can hook up a cheap MFR planter/harvester, or use a safari net to corral your villagers? TC makes things ridiculously easy to mine...why bother with a quarry or turtles if you can just grab a hammer. DartCraft has already been expounded upon at length on how cheap that is to do things.
And then there is the supportability of these mods in a server environment. I am convinced that they are all built for single player. Most server operators use some form of bukkit plugins for grief prevention. When you have server issues with an FTB pack, one of the first responses I regularly see is "sorry, we don't support bukkit, that's your problem".
Server load and permissions are another issue. If you run an open server, or even if you're closed but with a healthy user base, things like quarries, or elaborate machine builds where pipes are all over the place - like the OP has mentioned - just kill a server because most users can't police their builds. Having one user with an overflowing quarry spitting stuff out is one thing, but having the same with 5 or 10? All with chunk loaders? All with spawners? Our server has disabled several things like quarries, MPS, MFFS because they are OP, have nerved others for same reason, and disabled others because of stability issues (wireless redstone, etc), which in itself ends up limiting folks who are using a pack like Unleashed.
Compared to Ultimate, I created a relatively compact and efficient (on paper) base in Unleashed and regularly had worse frames (under 15FPS) on a pretty good computer. Problems like these force people to do less creative things with these mods so end up with a pulverizer, hopper, and large chest. Perfect example...that same setup, I built a nice tower with two multifarms, one to harvest wood and saplings, one to harvest papaya for efficient ethanol production. This was all going into my AE system to get processed as coal, etc. to fuel four railcraft high-pressure boilers, two of them liquid, two on charcoal. I did this so I wouldn't just go straight to ultimate hybrid solar panels or suck the Nether dry of lava. After two or three months of nightmarish problems with the boilers exploding for no reason whenever I re-entered an unloaded chunk, I ended up converting that entire setup and abandoning the farms and ethanol production and just went with 10 hybrids going into a bunch of electric engines. That is hardly a creative build, but there are tons of examples of bugs and problems that either limit your options, or suck the creativity out of people and they end up going with the easiest solution. I should point out, to encourage people not to go directly to hybrids, since they are so cheap to make, on our server they only output 128 EU instead of 512. I get much better frame rates now without that system, and nothing blows up.
Packs like Unleashed are not designed around balance, at least that's how they feel to me. It's like a bunch of mods were chucked together that people wanted, without thought to actual gameplay, which, agree or not, is where I think GT had the most impact. It made you consider progression. Things like Twilight are a cakewalk because people can go there with Nano or Quantum suits and fly everywhere. There's no challenge...just another thing to check off the list. Removing armour like Nano and Quantum and MPS would help... And I'll admit, that's a playstyle choice, but when playtime in a given week is limited, that goes out the window and it becomes whatever is easiest to do the job.
When it comes down to it, things have gotten too easy to do with the 1.5 packs, so pick the easiest way (there's tons of tutorials) and play for a couple of weeks, then get bored. Or go with a private pack and try and balance things on your own or add different mods to keep things interesting.