Copying this from another comment /edit: all of these updates are coming to the base game
TL;DR: This is not a DLC. This is Cyberpunk 2.0.
• virtually every system of the main game has been changed and/or updated
• police system is completely reworked with multiple tiers of NCPD/mercs chasing you down in vehicles according to your wanted level, apparently on level 5 maxtac will chase you down and it will be some sort of bossfight against them (source: https://www.youtube.com/watch?v=riK1i8lQwRM&t=511s)
• perks and skills have been completely overhauled, no longer simple passive stat boosts, much more active abilities like different melee finishers, a dash, or the ability to deflect bullets with melee weapons
• the difficulty curve is reworked/rebalanced
• the loot tiers are reworked
• archetypes of enemies have been redone for more variety in combat encounters
• an entirely new 6th skill tree that uses a different type of skill points (relic points) that will be used to add new abilities to your cyberware
• installing cyberware now has an effect on your body and you cant install too much or else you will go cyberpsycho (no idea what that looks like in game)
• installing cyberware now has a first person cutscene added to it, just like in the prologue at Vik’s clinic
• you can now “attune” cyberware to one of your attributes, making it more efficient if you have invested in that attribute; example here optical camo is attuned to the “cool” attribute: https://i.imgur.com/1UI9SEX.png
• armor is no longer tied to clothing, it instead tied to your cybernetics
• vehicle combat is added to the game, you can even use your katana on your bike
• vehicles are no longer bought from fixers, but bought through a website set up by mama welles
• some vehicles have guns installed on them (machine guns, rocket launchers)
• new type of infinitely replayable/repeatable missions are being added where you need to steal certain vehicles marked on your map
• new activity introduced “airdrops”, loot caches that drop randomly on the map that you can fight over and retrieve for yourself
• tons of new random events/activities are added to make the world feel more alive, like car chases and gang fights
The game is pretty stable at this point. I personally loved it, but it helps to set your expectations. It's a story-driven game with diamond-style story branching ala the Witcher 3, with a heavy focus on narrative. The world is an awesome backdrop, but it is more backdrop than simulation. It's not GTA.
Given how massive this overhaul looks, I would honestly wait for the 2.0 patch. It looks like it's going to address a lot of the shortcomings of the mechanics.
I didn't like it, I played about 10 hours or so.
It just felt like a worse version of Deus Ex mixed with GTAV.
I had some really bad bugs too like enemies seeing through walls on missions and immediately triggering alerts and combat.
I'd rather just re-play Deus Ex: Mankind Divided (or even the original).