Nice: new lighting, ragdoll animations, more tools/weapons to play around with, blunderbuss useful.
Not nice: flattening the loot progression (I guess to make the blunderbuss useful) completed the game's transformation from fun and surprising, if janky sandbox to grindy, janky, unimaginative zombie shooter. Instead of locking character progression behind actual challenge (the early hub cities were a decent early example of this), it's locked behind grind. Finding a gun store doesn't matter because it'll have the same blunderbusses and stone spears as literally every attic in the town. Smash more zombies to make the blunderbusses & spears turn purple, smash even more zombies to magically turn them into modern weapons. It doesn't matter what quests you take, which POIs you raid, you're getting the same stuff over and over again anyways, all dictated by your gamestage number.
The weird thing is that early alphas strongly hinted at progression being challenge-based. If you wanted guns, you'd look for police stations or Shotgun Messiah stores, which had a better chance of spawning in city hubs, which were significantly more dangerous than the wilds or suburbia. You needed to prepare for that trip. Now you just run to the nearest town, and start clearing out random POIs because they all hold the same zombies and loot anyways. If TFP would have followed through on the ideas in those early alphas, they could've made tiered biomes and POIs , with resources and loot appropriate to the challenge. Players could then choose to take on extra challenge and risk if they felt like upgrading their stuff earlier than "normal". Now the only difference between biomes is how often you have to chug drinks or food, with barely a reason to ever leave the pleasant greens of the forest biome.
I hate to say it, but between the removal of several biomes, transforming most POIs into linear dungeon crawls with guaranteed loot rooms and having GS dictate what loot you can get, this game really lost a lot of its early charm.