LogFAQs > #933673553

Took this from the official Blizzard forums. Haven't bought the game myself, but this is the current top post there right now:

Features that were available yesterday and have been cut 12 hours ago:
Cross-region play (the custom game list is no longer global and you cant play with players from other realms, meaning its much harder to find players and fill game lobbies)
Custom campaigns
Clans
Player profiles
Ladder (ranked matchmaking, stats, automated tournaments)
Good, battle.net 2 1.0 chat system (you can no longer use commands such as /f l, /join; information on how many players are currently playing; list of communal channels; battle.net 2 news section; overall the chat system lost its soul)
Beautiful UI/menus (in reforged client the menus feel sluggish and less optimised; the chat box overlaps the menus, atmospheric 3D campaign backgrounds are gone, etc.)
Creative freedom in custom games (the WE EULA has been changed, adding a lot of limitations - everything you create now fully belongs to Blizzard, read more in other topics; censorship in maps and game names, for example a lobby called booty bay can not be hosted, even though its the name of an offical WC3 map, etc.)
Classic graphics in Reforged client look worse (shadows are missing, saturation is off, some spells/effects are missing)
RoC campaign is now using TFT balancing