So I played three sessions of 5e this weekend spanning about 13 hours. I'll talk about it without any obvious spoilers.
Game 1: Tanja, Lisa. Old friends.
Game 2: Tanja, Daniel, Jen & Joe (married), Melissa, Laura. Melissa is an old friend who had played an old playtest version (with other folks) over a year ago, about 3-4 sessions. Daniel is an experienced indie games player. Laura has some indie game experience with me. All are experienced D&D players except Jen, who had never played an RPG before.
Game 3: Tanja, Daniel, Steven. Steven is a hardcore D&D guy, and he'd played in several of my 4e campaigns.
Everyone used a pre-gen except Daniel and Melissa. Daniel made up a character before he arrived, using the PDF that's available. He played different characters in the two games. Melissa had her old character from way back in the playtest days. She revised it when she got to the house to bring it up to speed with the PDF rules.
Combat is fast! It moves about as fast as old Basic D&D (I am most familiar with Moldvay). I used the fixed monster damage option to speed things up from the DM side. All I had to remember was that a goblin has AC 14 and does 5 damage (melee and ranged)--done!
Initiative is still a bit of a pain. I'm not really convinced of its value outside the tactical arena of 4e or even 3e. 5e combat is simple enough that there's seemingly not much value to tracking initiative order. Really, all you care about is who gets to attack before the monster on the first round, right? Then it's back and forth between monsters and PCs. Maybe with multiple monsters at different initiative times, that doesn't apply exactly, but I'd just use the boss for initiative and let everyone else attack at that time. Haven't tried it in actual play. I am pretty sure it'd make combat a lot faster. What happens now is that players sit there, waiting for the DM to say, "Okay, Laura, what do you do?" If they knew it was the "player turn" for combat, they'd all just coordinate their attacks and shout them out, and no one would have to maintain the order. I use index cards with names on them to manage order and that takes a minute or two to set up at the top of the combat, which is sorta excitement-destroying. It's easier for me to roll monster initiative once, say, "If you beat a 16, then you're first," let them go, handle monster attacks, then go into alternating PC-monster combat for the rest of the fight.
The rules for surprise were--well, pleasantly surprising. Basically, anyone who is surprised doesn't get actions on the first round of combat. There's no special surprise phase. This means that two PCs might be surprised but the rest won't be. Or two of the goblins are surprised but the rest are not. Easy to handle.
Advantage and disadvantage are brilliant and fun. If you have advantage, you roll an extra d20 and keep the best. If you have disadvantage, you roll an extra d20 and keep the worst. Advantage and disadvantage cancel each other. Everyone loves rolling an extra d20! Disadvantage doesn't come up much, since players always seem to find ways to avoid it or cancel it out with Inspiration. Inspiration is the role-playing mechanic. Play to your specific personality traits (codified through Bonds and some other things), and the DM can award you Inspiration. I gave them a red gemstone to mark it. You only have one Inspiration point at any time. Spend it to earn advantage. I let players spend their Inspiration for advantage /after/ they rolled the first d20 (and failed). Probably not what the rule intends, but it makes them use Inspiration more often, which gets them to role-play to /earn/ Inspiration more often. I'd rather they were role-playing more than playing the tactical game of "should I use Inspiration on this roll?"
(more in a bit)