When I first played there was no auto-butcher or auto-kitchen, so when hunters killed something and bought it home, it would rot in the butcher's shop if you didn't notice, meaning all the food processing areas had to have airlocks to stop everyone going crazy from the stink. You could at least tell the dorfs to stay inside, so they didn't go recover the socks of their dead friend while he was still under the elephant. There had been cage traps for a very long time already, so the game was not hard, but the micro was nuts. It was easy to get the humans and elves to declare war for three seasons having a siege, but it was also easy to not let that bother you.
At some point there was cats everywhere, in every fort, catsplosion, and they were all loved by someone, so every time you dropped a rock anywhere a cat died and the fortress collapsed into a rage of despair at the loss. The game wasn't hard as such, but did often end suddenly in the middle of something.
Then there was caverns, and so I explored them a lot, and I died doing that, which made everyone sad and also want to recover the socks of their dead friends because I hadn't figured out burrows yet. I'm not sure when the civilian alert came in, but that was handy when I found it. Burrow 1: Safe. Has much less magma flow and automatic atom smashers and controlled flooding than the rest of the place.
For a while there was a fort with undead outside, I didn't embark on evil terrain for a long time after that, as it made dorfs crazy to see them, or fight them, and even the best outfitted dorfs would get horrible injuries once the undead skilled up.
Puke. There's old saves that are very green. Everything is covered in puke. The rain you see, it made dorfs puke. Which spread by walking, which made dorfs puke, because of all the puke. The entire surface was green, over the snow. There was also a lot of trolls at times.
Water got better somewhere along the line, I built grand water traps for invaders to wash them all into the caverns from just enough height to make them easy for the military to train on, after walling them all off, naturally. Everyone had permanently-broken fingers, but not many died of it. I think I ended up drowning most of those forts, it was around the time combat-speed came in and there was bugs made actual military work tricky, so if someone did get inside because I forgot to lock a door somewhere it was just easier.
I think dorftress actually got harder all the way along. It's automated in a lot of places but the production chains have exploded and you have to make soap of all things (wood, furnace, ashery, bucket, plot, farmer's workshop, quern, jug, soapmakers, a dozen different stockpiles ... oh, someone got hurt already, arghghgh), there's much worse things turn up than mere elephants and bronze colossus, and over-production of food isn't all that much easier to deal with than under-production now that we also have fashion and worship and more alcoholism problems to manage (and bards that want to leave right now even though it's a bit undead outside and I have no military yet and why are there so many missing dorfs).
It's just I went from being happy to be able to take on a couple goblins without losing half my fort to finally figuring out how to handle building destroyers without cage spam (after they overloading my cages in a couple forts) to building massive enclosures for grazing (and figuring out the new tree problems and getting it mostly automated) to claiming the caverns and trying to pick the right squad of heroes to take on each megabeast as it turned up (masterwork steel spears are awesome, by the way) and now I'm routinely magma-diving from day one so I can set up my early stocks down there and still make deep irrigated farms along the way for a laugh.
The Liaison drowned while running from the undead recently, but I don't think that'll be a problem, they used to never give you a new one, now they keep sending them and keep getting annoyed at you letting them die. I mean, I'm not ready to wall in the whole surface, there's too many trees, and the edges are tricky with the season changes, plus the river complicates things. I really should've started with an aquifer, that simplifies so many things on the surface.