Deadfire's really good, like a step up from PoE in nearly every aspect. And it looks amazing, too. It's got lighting effects, weather, day/night cycle, 3D vegetation, and other visual tricks that really make it pop a lot more than PoE did. Then it throws a ton of classes and subclasses at you, with dual class options! There's almost too much customization there, and you can dual class every party member not just the PC.
One of the biggest changes is the emphasis on exploration. I haven't dug into that too much yet, but your personal ship looks to play a pretty big role in the game as you do a lot of island-hopping, and the islands look to offer a lot of chances to mess around and see what's going on. Plus, there's ship-to-ship combat, but I only just got my ship back [the opening area leaves you stranded for about 3-4 hours before your ship is ready to go again] so I haven't had a chance to check that out yet.
Really feels like Obsidian took what they learned from PoE, and from experimenting with Tyranny, and put it to good use here.