One big change is that the first three Pikmin felt like a bird's eye celebration of the beauty of nature, where you'd only notice that you're actually a tiny little guy on earth (or a post-apocalyptic earth) if you really paid attention, or late in the game.
Whereas this one, with the camera change and constant human environments is the opposite - the fact that you are an ant-sized person on earth is the primary focus, and the beauty of nature is secondary. It's an interesting change.
One thing I expect from this game is a huge amount more content than other pikmin games. Pikmin 1 and 3 were very short. The levels were intricate as hell, but there were only what - 5 in each? Which made for a very replayable game, but not a long one. I think with rewind and no time limit, Pikmin 4 won't be going for that replayability factor, and I think we'll see a whole bunch of small-ish, not-too-complicated levels like the sun dappled terrace, alongside all the caves. It wouldn't surprise me to see 12+ areas like the terrace. I can't imagine the game having less than six of them.
As for the caves, they are very similar in look to Pikmin 2's (which is bad) but they are clearly properly designed rather than generated (which is good, and is the more important thing). I didn't get the sense of boredom from these caves as I did with 2's so I don't think they'll be a problem.
The biggest thing from the demo was that I was afraid Oatchi would overshadow the pikmin to the extent that he might break/ruin the game, but it doesn't feel that way at all.
Also, collecting treasure in Pikmin 2 was a chore - it meant nothing. You're doing a lot of similar work here, but the fact that you're ALSO rescuing crew members / civilians - and that said people unlock new features - means that there is still a higher class of item out there to collect, which makes the action meaningful again and dodges that Pikmin 2 flaw.
