1) Miner still not fixed and will cause overflow errors time to time if unloaded duaring mining operation with infloop inside canReachTarget (extremely boring, forced to use homemade fix with safecheck - additional short param that break loop after 17 recursions no matter internal conditions.
2) CFPack crafted FULL, this allow player to get completely free foam, since CFpack cost less then foam - its viable option to craft new pack every time, not refill old. (also this a lot faster then refill).
3) Improved fuel (with NBT tags) will oveflow jetpack... (or something like this, since itemstack damage capped at 32k and NBT go over 40k)
4) Jetpack dont work well in SMP, option to disable it completely anyone? (same for electric jetpack and quantum suit in nether) (nether actually very very buggy)
5) All IC2 machines handle shiftclick like vanilla furnace (fixed in 125) from hotbar to inventory and from inventory to slot, this is not good for personal safes and actually vanilla bug easy to fix.
6) Terramorfers are way too expensive and too slow, not usefull at all.
7) Flatification module dont have any range limit, it will eventually go off screen to unloaded chunks with interesting results... (possible on servers with low render distance)
Mushroom is nice but biomeset is crappy and inconsistent, it shoud set biome in AOE around itself after some time, not individual blocks in random pattern.
9) Option to select range for terramorfer in GUI will be very very nice, currently due hurge AOE only option to use terramorfer is to stay AFK near it for real days.
10) Crops trampling == facepalm, ever worse then before.
11) Wheat and flowers will die at night due lightlevel 12 req, extremely boring, this make wheat vanilla farming superior in every aspect, no trampling, no light req, actually faster, easy to harvest automatically, easy to replant, no risks of weed.
12) Ever with hydration and fertilation crops grow too slow to be point of interest for users, you may not leave them alone due weed and babysiting way too long.