I have a number of issues with the August playtest packet. Hit points are now a shill for classes. Damage output increases to keep up so that Wizards and Fighters can put out similar damage while one gets an inherent bonus to AC by the ability to wear armor and also more hit points, while the other gets a giant book to lug around and little protection other than running away (which they now can't do very well due to the comback of Attack of Opportunity). Attacks of Opportunity are penalizing characters who understand that fighting to the death is stupid and players who don't say, "I withdraw/disengage," before running away or shifting positions.
Hit points and damage output. Instead of gaining a bonus from being a rough and tumble class, hit points are distributed so that Fighters have the most, followed by Clerics, Rogues, and finally Wizards. At each level. Wizards, no matter how high their Constitution, will never reach the hit points that Fighters have. Give a Wizard an exceptional eighteen Con and a Fighter an average Con of fourteen (18 Con Wizard vs. 14 Con Fighter). WizardX has 8 hp at level 1 while FighterX has 12. Taking the parenthetical "or x" numbers from here on simply because it's only 0.5 higher than the average of the dice rolls. WizardX, with his extraordinary Constitution score, gains 7 hp per level. FighterX, with his average Constitution score gains 8 hp per level.
A difference of four points in Constitution just doesn't matter because Wizards are necessarily weak/easily fatigued/fragile/et cetera. Compare again to Rogues and Clerics and a similar trend follows: Constitution just isn't as important as class. Dozens of hit points just makes for longer time whacking away or an increase in damage output to compensate for the larger hit point pool.
The Fighter and the Rogue get bonus dice to damage and even more as they gain levels. Even the spells like Burning Hands were increased in efficacy from 2d4 + bonus to 4d4 on a hit or half damage on a miss.
The entire system promotes what I call the "hit point grind model." And that doesn't make for interesting role playing or problem resolution. Why try interesting maneuvers when leveling up will make your character more resilient and more powerful? When the swing of an axe is more powerful than dropping tonnes of rock, there is something wrong with the game mechanics.
Attacks of Opportunity. It means that there is no escape once melee combat has begun. Unless you are fighting a character/creature that you are faster than, you cannot escape a fight. It gives extra attacks to classes that are already good at what they do. Fighters and Rogues are already good at fighting, but adding Attacks of Opportunity just means that they get to make another attack in a round. For every enemy that disengages.
Five kobolds decide to run away and don't actually disengage? Five free attacks. All adding this rule does is penalize the people who don't remember to declare that they are disengaging and it adds another rule and complexity to combat when it isn't necessary and doesn't add anything. Just say that moving through a melee requires a Dexterity check and call it good. Attacks of Opportunity are just plain useless. It just doesn't make sense to have it at all.