Deus Ex: Mankind released on Xbox One, PS4, and PC today, and numerous users are reporting issues with the PC version of the game.
Steam's aggregate review stands at "Mixed" as of this writing. Points of contention raised on the game's Steam page and sub reddit include numerous technical snafus ranging from mouse acceleration that cannot be disabled to low framerates and, a perennial favorite, seemingly arbitrary crashes.
Some issues have been address in a developer post. Advice for performance issues includes updating drivers, disabling MSAA and Contact Hardening Shadows, sticking with 1080p resolution, enabling Exclusive Fullscreen, and cranking settings to High if you're running a GPU with 4GB of RAM.
A bigger problem lies in the functionality of Deus Ex: Mankind Divided's Day One DLC, the Covert Agent Pack. Available on all platforms, the DLC is apparently good for a single use—for a single character. Square covertly renamed the pack to Covert Agent Consumables Pack, tipping off fans to the fact that consumable bonuses can only be used once, by one character. Meaning, if you create multiple avatars, the first one to crack into your pre-order pack depletes it permanently.
You can get hold of other Covert Agent (Consumables) Packs... by purchasing them as microtransactions.
Square will continue to update the developer post on Steam documenting known issues and solutions. As for Deus Ex: Mankind Divided's Day One DLC, use it carefully.