As the DM of our game, I am very pleased with D&DNext. I feel it fixes a number of issues that I have had with all versions of D&D. The following are what I and many in the group felt were right (or required a minimum of tweeking).
Easy to GM. Like I mentioned in my report, I intentionally left the adventure and found that I was able to run an adventure rather adeptly. My only regret was that I did not have enough experience with the system to know that I could have pitted the players against some of the more challenging monsters included and would not have overpowered them. Subsequent playtests will correct for this.
Advantage/Disadvantage Worked Well. It is a simple concept and works strikingly well. It might even turn the guy at our table with terrible dice karma into a viable player (as long as he has advantage).
Spellcasters Felt Magical While Being Useful. One complaint about Pathfinder is that 0-level spells are near useless (acid splash deals 1d3 damage), however they feel magical (deals acid damage instead of just damage). 4e's take was to make at-Will spells work the same for spellcasters as for martial classes, making them less magical, even if the spells are more useful. This got both. Kudos to you.
Liked Class Options. Below are some of the liked class options. Fighter: ability to deal damage even on a miss. Cleric of Pelor: Healer's kit healed without requiring spells. Wizard: ray of frost, magic missile and shocking grasp being minor spells and being useful.
Having said that, there are some options that need fixing. The following are suggestions to fix and how to fix them from our playtest:
Int or Cha Saves. I'm sure it is just becuase it didn't come up in our game, but for the life of me, I can't figure out what would need an Int or a Cha save. In subsequent playtest rounds, could you include material that would require that. Also, if unintelligent undead do not have an Int score, do they get an Int save? That needs clarified.
Spiritual Hammer Needs Reworded. As I mentioned in my playtest report, spiritual hammer was poorly worded. If it is intended to an attack in addition to the cleric's normal attack, please state bluntly. It does state, "You do so as part of your action," but we did not have enough experience with the system to be entirely sure what that meant. We agreed afterwards that it meant that the cleric got her normal attack in addition to the spell's attack, but it should be stated bluntly that the normal attack can be taken in addition to spell's ongoing attack.
Some Type of CR System is Required. I'm not sure if 4e called it CR or not, but having XP being the only measure of how difficult a monster is was not easy. Even if the system is basically, "the level where fighting only 1 of the monster is most appropriate" where it is known that if you have the entire town militia helping you (like in the L&L article), the group can take on a higher difficulty monster or if there are more monsters, you can fight them at a higher CR. But some quick and simple method of determining how many monsters should be that does not play in the 100's (like XP does).
Special Note: I would like to mention that I did not comment on the dwarf cleric since it was obvious that the character was built with more role playing and teamwork in mind (knight background, guardian theme) and it went into the hands of the one player at the table that neither role playing nor teamwork were his play styles. The character was suboptimal for him and I do not feel it is fair to evaluate that character except to say this: I looked over the character and saw nothing wrong with it. I am sure in the hands of a more role playing, teamwork friendly player, he would have excelled with that character. But the player was late and that was the last character available. Having said that and the fact that he is a full Pathfinder convert should make this statement all the more meaningful: even he had positive things to say about the system.
After Thoughts. I liked this game. Alot. I do like the fact that it is not assumed that the ability to hit did not increase with level. I am hopeful that it will make GMing at higher level easier since a larger bredth of monsters will be available and numbers will not get crazy high. This fixes a number of complaints I have had about D&D 3.x, 4e and Pathfinder all in one swoop. While there are still rough edges that need to be smoothed out and higher level play needs playtested, I like where this is going and am far more excited now about D&DNext than I was when it was first announced.
May the force be with you.