I'm wondering if we should maybe make a complete list of differences in rules. Not because I think that there can't be any differences, but just for posterity.
So list differences you've found here, and I'll edit them into the top post. If there's something that people generally feel the Devs need to rethink I'll add notes.
01. Mage Hand requires Concentration(it does NOT in the PHB), but it can also now shove/interact with enemies (which it couldn't do in the P&P version). ~ (So buffed and balanced against said buff?)
02. Firebolt is now 1D6 + A chance to catch fire instead of 1D10 (Might be considered a slight Buff).
03. Ray Of Frost now creates an ice surface that can knock enemies prone (Buffed)
04. Acid Splash has been changed to an AOE attack that reduces AC by 2 (a considerable buff).
05. Wizard's can learn any spell (hopefully a bug)
06. Can get sneak attack with Great Sword (hopefully a bug)
07. Food heals health (hopefully a bug)
08. Scrolls can be used by anyone (hopefully a bug)
09. Grease is flammable (Have to test myself, Sage Advice, states it is not, might be an intentional buff / return to older rulings on Grease, also it might just make the spell that much more useful).
10. Automatic Passive Perception Checks are missing (this is something I think should be addressed sooner rather than later).
11. Darkness has an arbitrary block on firing ranged into and out of it.
12. Devil's Sight warlock invocation does nothing, since even with it, you are still blinded in Darkness.
13. Sleep spell has been changed to a fixed amount of hit points (16 + 8HP Per Level). in the PHB it says "This spell sends creatures into a magical slumber. Roll 5d8; the total is how many hit points of creatures this spell can affect.
14. Rogues do NOT get Expertise at level 1 (which is a bummer, I think that should be changed to be more like 5e P&P).
15. Rogue Cunning Action has been nerfed to only be used for DASH (which is also a bummer, and I also think that should be changed to be more like 5e P&P).
16. Spears should be VERSITILE Weapons (They are only Two-Handed in Open Access, and it really serves no purpose mechanically).
17. Dipping/coating your weapon takes a bonus action instead of an action. Also you can use fire to add 1d4 fire damage instead of poison. (Yes, Basic Poison is described in the PHB and explicitly says you can coat your weapon with it as an Action for additional 1d4 damage added to the attack.)
Also many actions missing like Dodge, Help, Ready, conventional Disengage...
Also many enemies have entirely different stats and abilities.
Height gives advantage, being further down gives disadvantage.
Sneak attack doesn't work at all like it does in PHB.
Shoving should allow to make enemies prone, but you can only knock them away.