May I take the time to point out that I hate, hate, hate the switch from writing distances in squares instead of feet?
(By the way, major rant warning)
Squares are an artificial game concept in order to enable some order to the combat simulation. They don't actually exist in the game world. Making "squares" the standard distance is equivalent to changing the standard unit for weight from "pound" to "turducken". It's one thing to suggest that DnD is a tactical combat simulator instead of a role playing game, but switching to squares just seems to go too far. Now, instead of knowing that something is, say, 315 feet away, I'm told that something is 63 squares away and have to actually do math to figure out what that means to my character in-game. It's a subtle way to emphasize that 4th edition has made Dungeons and Dragons from a Role Playing Game to a roleplaying GAME.
Having to do mental calculations just to translate "game-y" mechanics into an accurate description of how far away something is as my character sees it is not a move in the right direction IMNSHO.
Complaint the second: the way they write out the ability scores and then conflate the skill bonus with the ability modifier. There's no real reason to do such instead of just having a separate note that all skill checks have a +13 bonus from level. It's rather like listing the reach of a creature in the "Speed" category. Could it be marginally useful? I guess, but it's not intuitive in the least. Also, a lot of people don't necessarily know that a 32 Str is a +11 bonus, or at least don't know it off the top of their heads. It'd be nice to still write out the actual ability modifier (which is far more important than the ability score, since the score is just a device to tell you what the modifier is).
Third game mechanic complaint: "saves." Why does every debilitating ongoing effect in the game have a 50% chance of getting thrown off, regardless of level, ability scores, saves, or class? Why does the 1st level wizard with a 6 Con have the exact same chance of throwing off the poison in his veins as the level 30 Fighter with 20 Con? It also greatly reduces the ability of a player to differentiate his weaknesses from everyone else.
Another minor quibble: I don't understand the point in keeping in fear effects if the only thing they do is give everyone a -2 to hit? No save, no variable effects based on class/hit dice/ability scores. Just a flat -2 to hit for everyone. Why not just bump up the AC by 2? It's the same effect that's far easier to track and remember.
Last complaint of the night: what exactly is the point of "Pit Fiend Frenzy"? You can either spend a standard action attacking with your mace, or a standard action to attack with your stinger... or you could ignore both of those options and just take a standard action to attack with both.
Sorry, that was one big long rant.