Races
I don't mind what races are included. I like the old and the new. Make races count across levels. Feeling different is more important to me than game balance. I agree with earlier post re making the bonuses bigger and continual. AND bring back penalties! On that...
More Penalties
Bring back penalties. I do not like 2 ranges (with one penalty). Bloodied should mean something. I don't mind if the numbers start out easy and get worse with damage. Saga condition track was on the right track. On a similar note....
Being able to do everything all the time
I am OK with the 3 actions a round. What I don't like is taking away all those nuances that players loved to discover or were logical/story related mechanics. Blunt weapons doing more damage vs skeletons. Rogues having a hard time critting constructs, etc. It is fun to make discoveries and decisions based on logic (not game rules/math) in the game. No one bothers with a hammer vs skeletons b/c arrows do the same

Sorry, but I don't find being able to do everything all the time fun. I liked when you got to say 'That is a cool idea', and there is a mechanical effect. (Blowing heads of zombies in Savage Worlds gets it).
Class Powers/I want a game I CAN write for
I loved the class powers at first, but quickly grew bored with them. Some do way too much (given you already have 3 goes a round). Too many don't seem class specific. Same effects with different descriptions. I loved alternate 3e classes and writing them myself, or at least adding options/changes. It is next to impossible to design a 4E class yourself. A LOT of work and little chance to get it right. Also there is a lack of continuity of the powers - doesn't seem like getting 'better', just something completely 'new'. Characters can have a complete grab bag of powers at moment and one power can be replaced with a completely different one - I liked the improved versions of Talents. And so much work having to plan multiple powers up to 30 levels? Even the writer's Guidelines basically tell you not to do it! Personally I reckon Saga got it right. Loved Talent Trees (and I can see a correlation with the wonderful ideas on Themes being discussed above) and this was my favourite thing I thought would make it into 4E from a players perspective.
Keep the monsters
From a GM perspective I concur with many others in stating keeping the monster stat blocks similar to what they are. No referencing other materials is great, as is being creative with unique powers. Just tone down the hps though.
Conditions = Good
I agree with keeping saves etc for ongoing effects, but not everything should fit this. Should be another system similar to Disease rules for some conditions too. Poison could easily be a round to round thing or a day to day thing depending upon the poison. Should NOT just be damage.
Make Power Sources Count
I love power sources, but make them more distinctive, especially rules-wise.
Keep the Story
Don't try and rewrite the Planes, Creature origins etc again. 4E finally nailed a very good cosmology and I love the links between creatures, home plane and power source.
And finally...
Designer Friendly
Like classes above - provide some core examples, but more on advice and tools to help a GM develop their own races, classes, settings, subsystems etc. Give Chris Perkins a job here. Random charts are always good here

Must have an OGL too. basically I want a game I feel I can contribute meaningfully to. I really struggle to find 'space' in the 4E system.