Trees have multiple tiles and chopping a half dozen could easily yield over 100 logs if you're careful about designations.
Fruit-bearing trees can be harvested using step-ladders at a plant gathering zone- so you might want to not to chop anything that drops deliciousness.
Seasons! Like, the switch from winter to spring is just the most dramatic thing ever with a burst of color all over the ground and flowering trees. It's very pretty.
Related to that, plants have specific growth cycles and seeds can't be harvested until after they've been left alone for a while otherwise you'll just get leaves.
Climbing and jumping have both made it easier to adventure and harder to play an above-ground fort. Like, if you just have a 1-z wall then goblins will hop over it like it isn't even there; in order of easiest to hardest to climb: ramp>natural wall>boulder/log wall> block/bar wall>smoothed natural stone (This last one requiring flight).
Meanwhile dwarves that get spooked might climb the giant trees and then to true dwarfy fashion forget to climb down when they get thirsty and just die up there. Same thing happens to farm animals.
Needs and desires got revamped, so you actually need to pay attention to the civilization's culture somewhat to keep things running smoothly for more than 5 years. The dorfs will tolerate a lot of abuse at first, even sleeping on the ground for years without complaint if need be, but later it'll take more than a legendary dining room to keep them going efficiently. You'll need to use {l}ocations (a subtype of meeting zone) to designate parts of your fort as temples, taverns, and libraries, where the population will gather to do all their spiritual/social/philosophocal fulfillment stuff.
Visitors will sometimes arrive, mostly bards and poets but sometimes you get lucky and attract a monster hunter or a mercenary. At least one redditor has witnessed a diplomatic meeting at his fort between the elves and humans- it consisted of the representatives spitting at eachother in his tavern and dodging saliva for ~3 years until the elf got hit- then they both left. It was magical to read about.
Sometimes a visitor will apply for residency, which serves as a stepping stone to actual immigration and therefore means fortresses can involve more than one species! Very exciting for anyone that's ever wondered how much havoc a rhinoceros man decked out in full-steel could wreak on copper-armed goblin hordes. (The answer is a lot.) You can increase the likelyhood of this by assigning some bedrooms to one of your taverns for long-term residents to stay in and feel like home.
Libraries can impart skills and personality quirks to the reader with a good enough author writing everything, skill increases have only been confirmed for the medical skills and brainwashing requires that they read nothing but similarly toned books, but it's still a very good reason to well-stock a library IMHO.
Zombies got nerfed and blunt weapons cause "pulping damage", roughly the same thing but pulping generally works on anything fleshy living or undead- and since zombies no longer function on gamey hit-points but instead on how intact the moving parts are hammers got way more useful as a way to put anything down permanently. They're also pretty stupid and just charge at whatever with zero regard for whether this will make them crash into another zombie- which makes them pretty easy to out maneuver if you're fast enough.
You can set priority on designations, from 1 (immediately) to 7 (if there's nothing else they feel like doing) which means you can set multi-z pits to be dug without worrying that one of the idiots will cause a cave-in and other awesome projects.
There's a ton of other stuff but those are the most (hehe) game-changing things.
