Mr Jack said:
4E should be sufficently different from 3.5 to be a recognisably different animal but at the same time it must still be D&D, which to me means: classes, levels, six ability scores, slot-based magic, arcane-divine magic split, magic items, xp for killing stuff, hp, and armour that makes you harder to hit.
With one exception, I agree very much with Mr. Jack here; that exception being slot-based magic and its corollary annoyance of spell pre-memorization, which is and always has been a very cumbersome way of handling spellcraft. I'd far prefer some sort of spell-point system with at least a part of the s.p. rolled at random a la hit points; the same rationale applies, that not everybody has the same capacity to cast spells even if their intelligence scores etc. happen to match. Then, you can cast x amount of y level spells per day from anything in your spellbook, much like a Sorceror works now except for the spellbook. (nice side-effect here would be that Sorceror could be ditched as a class and folded into Wizard; it's a redundant class if Bards are kept)
I also very much like that Mr. Jack did *not* include as essentials skills (too many, and available to too many classes), feats (annoying, but a powergamer's delight), and other 3.x inventions that have added complication that outweighs the flexibility they also add. Prestige classes are another reasonable idea that has grown into a complete nightmare; at last count there's over 1,000 been published, far too many!
One essential I'd add to Mr. Jack's list is saving throws. That said, the Fort-Will-Refl system is almost too simplistic...some saves should be based on Int. rather than Wis. (e.g. Illusions, charm effects, psyonic attacks, etc.). One basic mechanic that needs to be dug up from the grave is the idea of a save or check being to roll *under* a given stat., e.g. a Dex. check to avoid falling into a pit. Side benefit here is that every point in the stat makes a difference, rather than only even numbers mattering. If your stat is 20 or higher (another gripe; how can what starts as a 3-18 bell curve lead to so many characters constantly having at least one stat in the low-mid 20's?) then a 20 always fails.
One other thing that has slowly been becoming more important over time, and that needs to Go Away, is spell schools (the old-timer in me says "other than Illusion", but I'd like to see Illusionist become its own class again) particularly as applied to divine magic. By all means, though, keep spells somewhat deity-specific.
I could go on...and on, and on...but instead I'll simply congratulate you if you've read this far, and carry on ranting some other time.
Lanefan