First two sessions of DM with a bunch of guys who hadn't played D&D for a while. They usually play more complicated RPGs or tabletop wargaming. We had a blast, and everyone agreed that the rules were straightforward, yet realistic enough for our taste. I could focus on the story.
Rules that were just right
The Advantage/Disadvantage system: I was sceptical at first when I read the rules, but in practice it worked nicely. Also, I saw the players change their actions based on Advantage/Disadvantage, whereas players don't change their actions for a + or – 3 bonus.
Skill System: the best new part of the 5th edition. Simple, easy to use in different situations. Intuitive for both DM and PCs.
Both types of Clerics were fun to play and seemed balanced.
The rogue was very interesting in combat.
As most people pointed out, combat was fast. Also, it was nice not to have to use a battle grid/miniatures (if you don't want to). Since the rules are simple, it was easy to improvise during combat (which I tend to do).
Monster design: I like a nice simple layout, one or two abilities per monster. Same thing for the spells: they were presented in a simple format.
Rules I don't like
Extended Action: how to you go about a task that is not a pass or fail test, but that is a more progressive. You could do it with multiple Skill Checks, but I don't like it so much...
Characters helping each other: Regardless of your Skills/Ability Scores, you always grant an Advantage to another Character. That doesn't seem right, especially when you look at a character with no skill training and average Attribute compared to a skilled character with above average Attribute.
Looking forward to test other class/higher levels with the PCs!