The first world I genned in the new version ended up being pretty much dead. I had let it run for 300 years and most of the megabeasts died off early, but there happened to be a necromancer tower.
Embark warns me my civ is dead or dying. Expedition leader is immediately promoted to king, and another dwarf becomes expedition leader. Light aquifer was easily breached and walled off, and I began to dig out my fort in layers of chalk and marble below.
Not a single caravan shows up. The hard-coded migrant wave gives me 2 dwarves. A siege of around 7 necromancer experiment archers shows up. (I was initially worried that they were demons from a worldgen "dig too deep", since they were called "Demons of E-<something>", but I remembered demons don't impersonate horses.) I didn't have any idea how tough they are, so I seal off my fort with some logs and start smelting all the iron ore I've got so I can forge equipment.
Unfortunately, I didn't store enough logs in my fort before I sealed, and most were wasted fulfilling the king's mandates for barrels. I decide to search the caverns for mushroom trees. First cavern is barren with no water or vegetation. Second level same thing. I hit the magma sea and there's no air above it, just rock. I decide to dig into a candy spire from above, just for the hell of it, and eventually end up unleashing the circus. I activate my civilian alert and my miner flees back to the fort and I lock the floor hatch behind him. Demons start an endless war with the cavern animals that enter the map.
I decide I've got to kill the experiments to get wood, so I draft my two unarmored miners and unseal the fort. The experiments didn't leave their corner of the map (where they'd been shooting the surface animals earlier,) so I probably could've grabbed some logs an made some armor. I was out of patience by this point, though, so I send them to battle. They receive major injuries from arrows during the charge, but make short work of the experiments with their pickaxes. I get the hospital set up and treat them. I unlock the cavern hatch and retire the fort, deciding I'll take the demons on in adventure mode.
The only option available is human outsider, so I go with that and have him start in my retired fort. The game immediately crashes. Turns out there's a bug with outsiders in the current version, so I decide I'm done with the world. Given the frequent crashes during worldgen, I'll be waiting for 0.47.02 to start again.