Okay, I'll play too...
My 4e Wishlist!
1. No more "One hit wonders"!! Save or Die/Nerf magic and abilities get the boot. No high level character (or even mid-level character for that matter) at full health should have to worry about being taken down by a single roll unless the foe they are fighting is far out of their league. Incorporate some kind of mental HPs perhaps that can absorb Will Save/Nerf spells as "mental damage", powers, etc. I'm actually trying out a concept called Resolve Points which does exactly this.
2. In the same vein, tone down high level damage. There is too much damage being churned out at high levels and this creates battles that are highly initiative dependent and potentially all too short. Make it harder to die, and harder to come back.
3. Compress the disparities between the PCs. Armor Class, Attack bonuses, Hit Points, Saving Throws, Stats. Remove stats bonuses from Spell DCs. Higher level characters become too polarized in power - they can make their good saves, but their weak saves become increasingly difficult to impossible. If you create an encounter that will challenge your Barbarian, your Wizard is often 1 round roadkill... and simliar issues.
4. Reduce dependency on magic items. Obviously, I can see that many others share in this desire and for the same reasons. Tone down the spellcasters to compensate. If you compres the disparities between the classes, the wizard won't require as much power to keep him on par with the other classes.
5. Either dump or offer other options in leiu of Vancian Magic.
6. Roll back the number of powers a single creature can have. Some monsters are such stat abominations that you have to spend considerable time just trying to figure out how to run them in a halfway intelligent manner. On top of which you have to try and not forget that it has X, Y or Z power that could be crucial at some point during the encounter. For example, no monster should have default spellcaster levels on top a horde of other special abilities, tactics and feats and then mental stats in the 20's, 30's and 40's on top of this.
7. Classes - I don't really care how it's done, just make them balanced and playable at high and epic levels. And part of being more playable is for the game to be more predictable at high levels. The less the DM has to worry about game balance, the more time he can spend on the campaign itself.
Cheers,
A'koss.