The TL;DR Version

The full, official release notes for the v2.0 update are attached at the bottom of this post. It details all of the changes to BG:EE, BGII:EE, and the Infinity Engine as a whole. It also includes a section that's just for modders talking about some of the new opcodes, triggers, and actions that the update adds, as well as a collection of guides to help UI enthusiasts get their feet wet tinkering with the new UI system. The document clocks in at just over 30 pages; you won't want to miss it.- New Class: The Shaman- New Cleric Kit: The Priest of Tyr- Class Ability Tweak: Poison Weapon now scales with levels- Item Tweak: Stupefier +1 has been adjusted to be more in line with the game's other equipment- Spell Tweak: Enchanted Weapon now modifies the target's existing weapons- Items can now be placed in the Off-Hand slot while ranged and two-handed weapons are equipped- Steam Cloud Save support has been added (Steam only)- Achievements have been added (Steam only)- The User Interface has been overhauled with a new system- Dozens of modder-friendly enhancements- Hundreds of bug fixesThis is our biggest update ever, and it applies to both Baldur's Gate: Enhanced Edition and Baldur's Gate II: Enhanced Edition. We have a lot of improvements planned in the coming weeks and months as well; stay tuned for more information!