Blizzard has it listed as infrastructure changes and memory optimizations. It appears that the vast majority of Linux users are unable to connect in game, although the Battle.net launcher has no problem connecting. Here is the full BattleNet.log file. I let it sit and try to connect for a little over a minute and you can see in the log file that it generates and error almost immediately after attempting to logon.
3/23 06:53:33.209 [IBN_Login] Starting up | hasFrontInterface=false | hasBackInterface=false
3/23 06:54:00.407 [GlueLogin] Starting login | launcherPortal=nullopt | loginPortal=US.actual.battle.net:1119
3/23 06:54:00.407 [GlueLogin] Resetting
3/23 06:54:00.407 [IBN_Login] Initializing
3/23 06:54:00.408 [IBN_Login] Attempting logon | host=US.actual.battle.net | port=1119
3/23 06:54:00.409 [GlueLogin] Waiting for server response.
3/23 06:54:00.561 [IBN_Login] Front disconnected | connectionId=1 | result=( | code=ERROR_OK (0) | localizedMessage= | debugMessage=)
3/23 06:54:00.561 [GlueLogin] Disconnected from authentication server.
3/23 06:55:04.084 [GlueLogin] Explicitly disconnecting from realm server
3/23 06:55:08.099 [IBN_Login] Destroying | isInitialized=true
3/23 06:55:08.638 [IBN_Login] Shutting down