As a GM of 20 years experience I continue to be amazed by players who think they can predict what a campaign is going to be about, or even worse, what it's ought to be about.
As a GM of nearly 30 years experience, I take for granted that my players will have a say - to some extent, a key say - in determining what the campaign is about.
I don't normally do this the Burning Wheel way - which is to expressly discuss all this stuff in a "campaign set up phase" involving both players and GM. Rather, my players do this by making choices about their PCs' builds and background, their PCs' development, and their PCs' actions.
The magic item rarity system, however staggeringly incompetent one may find its execution (I do), managed to address a real issue: WotC authors could no longer write up mysterious magic items, because whoops-de-doo they'd end up in the player's finger tips before GMs even had a chance to make room for them in their campaigns.
I'm one of those who doesn't like the rarity system, and preferred the original method of handling "GM only" items, namely, artefacts.
Give us an edition where D&D is about campaigns which PCs can play in - and end this nonsense of special snowflake PCs which DMs have to design campaigns around.
My preferences are just about the opposite of this. So I would prefer it if the new edition at least tries to be neutral on this point.
Has it gone too far in 3e and 4e? Yeah, I think it has, but part of the problem too isn't just the "special snowflakey-ness" of feats, powers, and skills---it's that they make adjudication and NPC creation very messy and time-consuming. If WotC could keep special snowflakes, but make it easy to streamline the the results, they'd be on to something.
I don't have much trouble building NPCs for my 4e game. I gather that 3E can be a nightmare, at least at mid to high levels, but it's system for NPC building is quite different from 4e's.
I would love to go back to the days when character building was not as complex as it is now. Back then players looked up from their character sheets more and didn't have to flip through rulesbooks as often.
I can't comment on character sheet referencing - the character sheet has always been pretty imoportant in my games, both D&D and others, because it has the list of equipment, items, spells, abilities etc - but the need to look up rulebooks in 4e play is pretty minimal. That's a design goal that was achieved, and it would be nice for the next edition to replicate it.
This game will be roleplay-heavy and combat-light. Please tailor your characters accordingly.
For a combat-light game, I honestly wouldn't use 4e, or indeed any edition of D&D, or indeed any mainstream fantasy RPG.
My game is roleplay-heavy and combat-heavy (as in combats in probably 9 out of 10 sessions, and often more than one per session). This is the sort of game that I find D&D, and especially 4e, to be well-suited to.