Ok let's see:
All my experience is from UV till now:
New Hell's Arena:
Pretty much nothing changes, only that the new layout makes it somewhat easier to cornershoot. It's easier but the fact that it's on 2nd level and not 3rd (not sure if that's always the case) actually balances it somehow. No complaints.
Chained Court:
Pretty much easy as always since you got the hang of it from earlier games. Liked the fact that the modpacks now are harder to get, and they are also random I assume? I do miss the agility mods for tactical boots, but I guess random is fine too.. No complaints on this really.
Phobos Lab:
Great unique layout. I liked it. Nightmare Demons were REALLY scary at this point in the game, and they were too many. The surprise when returning from a lever was also terrifying with the walls that opened up. Had it not been for Cateye it would be certain death. Quite hard without a phase device for so early in the game... Scared the shit out of me at that point, so it's obviously nice in terms of challenge at least.
Deimos Lab:
Great work too. Loved all the level though the 2 shamblers are a bit overboard especially for lowest difficulties ( I can sympathize with complaints in HNTR/HMP) but I guess since it is an optional level, the challenge is great since the reward is about some of the best mod packs in the game. Some builds will have it incredibly hard against the two regenerating fiends.
At least they can be skipped along with their rewards.
The Wall
This was moved to level 11 from 7. It was a hard special level, but the reward of backpack plus launcher always made it tempting. Now that it's on 11, not only is it much much easier since it is the exact same level, but also makes the player run out of ammo in a way, so that city of skulls right after, becomes harder to visit. Can't say I really liked this change 11 seems kinda late. Also makes the anomaly harder since no missile launcher there now.
Halls of Carnage:
Quite hard. Probably the biggest difference by far from earlier version. The lava runs like crazy (srsly!), the monsters have doubled or tripled, there is no time to do anything. Had it not been for my antigr. boots & MCe, I would have probably died before getting to the exit. Too dangerous without a homing device.
Vaults:
Nothing changed seemed like the same thing. I guess it's ok it didn't really need any changes though I find it quite strange, the fact that there are so many Archviles on the left and they practically never have anything to resurrect. By the time you get to the revevants on the right the Archviles are already dead. This makes it quite easy in fact and silly to boot. Monsters should be mixed to have proper difficulty. I wonder why no-one mentioned this.
Limbo:
Great, nice idea. I do think though that's it's very easy compared to Mortuary. The reason is simple. Due to loads of lava, the monsters don't have that much space to move and resurrect. Furthermore you can knockback most of them in lava. I also assume the corpses are much fewer than in Mortuary which is natural due to lava once again. I entered the level and had 6 archviles from the beginning surrounding me. While this makes it a hard entrance, 2 bfg shots from the get-ago practically finish the whole level this way. Or at least most of it. Isn't that right?
Mount Erebus:
No complaints pretty much a great alternative to Lava pits. Liked it for the time being.
Cyberdemon/Mastermind:
Didn't notice any serious differences but maybe it's just me.
