KnyttInGod, I don't seem to agree with anything so far that you claim to be popular opinion. I can only suggest that when you post, you ensure that you post in a way that confirms that perhaps only you feel this way. It's usually a better bet. So take this with a grain of salt, but..
I appreciate you taking the time to say what you didn't like about KU, but.. I think the attempt at explaining it turned into more of a complaint than anything helpful for Nifflas. He doesn't/shouldn't need to be told how to make his next games. I realize it's tempting to try to inform him of errors you personally find, but make sure you do just that- inform. The other thing to remember is exactly what I said- make sure you do it in a way that insist it's your opinion. He's more likely to listen (even in a small way) if you're giving advice, not actually discrediting his previous job(s) at it. People really don't enjoy being told that all the work they spent is disliked, and much less so if you're telling them how to do it 'better' by your own personal opinion.
As for the graphics, it's a different style. It's fine for you to think the old style was superior, but it's important to realize that Nifflas was trying new things with this game. So the graphics a different than they used to be. It fits the game, in my opinion, and it's really tough to say that they aren't just as good as the old graphics, as far as quality goes.
Story is more or less the same thing. And as LPChip said, the story was always there, it just wasn't upfront about it. It's a different style game, and a different way of telling a story. If you aren't fond a deep story (that's 'hard' to follow), perhaps KU isn't for you.
As for your third point, there's not much to say there. Nifflas might release an editor- I don't know. As for quality, that's the tough part (and I'm not sure what you meant about difficulty meaning quality, since if you've played KS, you know it's untrue). Nifflas likes to make sure that things of quality are made for his games. How he does it is up to him..and even -if- he does it, is up to him. Your suggestion might give him ideas, but I don't expect him to follow it- neither should you, really.
Anyway, I'm sorry for seeming harsh at all, it's just that your posts seem somewhat expectant that Nifflas should accept your post at face-value, but the truth is that it's your opinion, and yours alone, mostly.
EDIT: As an added note, I should reiterate that there's nothing confirming a Knytt "4" yet, and there's no reason to really suggest things about something we can't be sure will even exist yet. (By the way, Knytt, Knytt Stories, Saria, Knytt Underground, The Great Work, (and some relation to the WADF games, too)...makes it more than 3 Knytt games therefore; not Knytt "4")