Since the playtest packet didn't include any character creation options, or even a good explanation of the attack bonuses listed, my response is going to focus on the actual gameplay. We just played with 1st level characters, so advancing might address some of the issues discussed below. When I looked at the advancements to level three, however, it seemed like most of these issues would still exist.
1: The out-of-combat healing is insufficient:
After each extended encounter the front line was down over half their health. A lot of time was spent convincing party members with half their health to continue the days adventures. Part of this was being used to 4th edition's healing surges which allow for going into the next encounter better prepared. The other part was the knowledge that one or two hits in the next fight would drop an already wounded character.
2: Randomly rolled out-of-combat healing stinks:
In the same vein as point 1, the fighter can vary from restoring 3/20 to 15/20 outside of combat. That is one hell of a range, and it's really unlikely that everyone who is wounded will heal back to a sufficient amount that they're willing to continue exploring. The 1/4 hit points of the healing surge is a good pre-defined solution, though I like including the constitution modifier. Maybe a surge would be 1/4 + conmod or 1/5 + conmod. Either way a fixed amount is good.
3 : Not enough In Combat Healing Options:
We're back to the cleric will spend most of their spell slots healing the party, and the healing doesn't scale with level and is not sufficient to compare to the damage the monsters are dishing out. At first level, the cleric didn't really explore the other spell options and went for two castings of cure-light-wounds. At 1d8+4 hit / casting, the cleric felt that her healing was weak. On a personal opinion note: I've always been annoyed how healing lost efficacy as the characters level. A spell that at first level would restore potentially half the health of a fighter, would only heal the barest of scratches at high level. I really appreciated healing word in 4th edition restoring 1/4 + 1d6 hp of health.
4 : The Advantage / Disadvantage system is simple and fast:
We really enjoyed the advantage / disadvantage system. It's quickly apparent that disadvantage really means it. The ranged characters did their best to avoid being adjacent to the monsters, even without opportunity attacks. We really liked that assisting granted advantage. It finally felt like assisting was worth the effort. The static +2 from 4th edition rarely makes the effort worth while. It flowed well, and didn't require much in the way of explaining.
5 : The pacing was very good:
This might have been a factor of the module and how things were laid out, but combats were quick. I think the biggest reduction was the removal of the plethora of interrupting actions.
6 : Good Riddance to Attacks of Opportunity:
The party can run away! Monsters can flee! Maneuvering around the opponents no longer feels like you're dragging your feet. The opportunity attack slowed down combat, and really made fights feel like they had to be fights to the death.
7 : Moved by movement:
We all really liked the new, simplified movement rules. The ability to split your move before and after the attack was lauded by the ranged characters. Being knocked prone is no longer one of the worst affects that can happen to you. No longer can you knock an enemy prone and shift away, preventing the enemy from hitting you the next turn.
8 : The party endurance was very bad:
With the healing points mentioned earlier, the adventuring "day" was 15 mins long, in game. Even if you exaggerated travel times, and time spent searching the bodies etc. it would at best be a single hour. It very much felt like the heroes only got to scratch the surface of the dungeons when they were obligated to retreat for the day.
We really enjoyed the chance to test the next edition, and are looking forward to test again. Thanks for providing the opportunity to provide feedback