I haven't really had a full play session of 4E yet, but have been reading the books like crazy, and am planning to run KotS soon for the family and one friend of ours. I'm also going to try and adapt War of the Burning Sky (from ENPublishing, yay) to 4E because I like the story, and feel that our group will enjoy it as well. I really don't want to try and DM that in 3.5 though. The conversion work will be tricky in spots, but I have plenty of time given the speed at which our usual group is wrapping up the 3.5 game. Famous quote from one of the usual group players, "Well we *can't* game two weeks in a row, so we'll have to schedule for 3 weeks from now". One of them also starts falling asleep around 9:30 pm on Saturday nights when we play. Ugh.
We've done some sample combats and such, but no real game yet. Nonetheless, I'm excited about 4th edition. I think that the skills challenges (once the math is fixed) are a great concept that will hopefully involve everyone more than the current system of "Just watch the one person with the high Diplomacy skill handle it all".
I'm excited about running a game for the first time in years. I'm also thrilled to see a lot of the Vancian magic go the way of the dodo. My hope is that we'll have fights where everyone is more involved, can take more actions, and the action is more dynamic. We'll have roleplay scenes where everyone is also more involved, and not doing a crossword puzzle while the bard handles it all. I like seeing first level characters that have a lot of choices in what they can do right out of the gate, and won't die from a single goblin tossing a spear at them and rolling a 6 for damage.
There are a few things about 4E that have me shaking my head, such as the alignment system. Why LG and CE but not CG and LE? Why not just go to Good, Evil, and Unaligned? Or keep the old way? Weird. Magic items are another one, since despite everyone telling me it's lower magic than older editions, I've never been in a D&D game ever where first level characters were given magic items other than potions, scrolls, and maybe a wand. All consumable items. I know our current 3.5 game is sub-normal in the magic department, but we don't have a wizard or a sorcerer either, so it's really not a typical 15th level group anyway.
Oh, speaking of playing 3.5 at 15th level, zomg is combat slow to resolve. We get to watch the paladin stand in one spot, with an occasional 5' step, and pound stuff with the 4 attacks that he's getting. The bard complains about how much she hates combat and there is nothing for her to do but sing the bonus song and buff us (welcome to the bard class), and I try to maneuver around, but can't really do as much as I would like with spring attack and such, and my sneak attacks won't work on undead anyway.
So for 3.5 combat, you seem to often have the quick and the dead. Meaning that if you don't get initiative, an attacker will get 4 attacks off on you before you can react. It's annoying to have the players 1-shot a tough monster before it gets a turn. Action deficit is the problem there in addition to initiative.
4E has more critters to fight, and no one gets iterative attacks. That should be a huge improvement in the flow of combat right there. I'm looking forward to trying it out some more.