Multiplayer
After joining a server world the client and server console console has some warnings
Unable to resolve BlockEntity for ItemInstance: minecraft:shield
That server was created in 1.2, running under all 1.8 versions and started with some 1.9 snapshots.
Client
[07:20:21] [Client thread/INFO]: Connecting to localhost, 25566
[07:21:11] [Client thread/INFO]: [CHAT] Saved screenshot as 2015-08-29_07.21.11.png
[07:21:37] [Client thread/INFO]: Connecting to localhost, 25566
[07:24:18] [Client thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shield
[07:24:18] [Client thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shieldServer
07:20:07] [Server thread/INFO]: Starting minecraft server version 15w35e
[07:20:07] [Server thread/INFO]: Loading properties
[07:20:07] [Server thread/INFO]: Default game type: SURVIVAL
[07:20:07] [Server thread/INFO]: Generating keypair
[07:20:08] [Server thread/INFO]: Starting Minecraft server on *:25566
[07:20:08] [Server thread/INFO]: Using default channel type
[07:20:08] [Server thread/INFO]: Preparing level "Molokai"
[07:20:09] [Server thread/INFO]: Preparing start region for level 0
[07:20:10] [Server thread/INFO]: Preparing spawn area: 45%
[07:20:11] [Server thread/INFO]: Done (2,411s)! For help, type "help" or "?"
[07:20:25] [User Authenticator #1/INFO]: UUID of player Kumasasa is 212c6adb-6aad-4b04-ab21-0d52a98931c0
[07:20:25] [Server thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shield
[07:20:25] [Server thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shield
[07:20:25] [Server thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shield
[07:20:25] [Server thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shield
[07:20:25] [Server thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shield
[07:20:25] [Server thread/INFO]: Kumasasa[/127.0.0.1:60409] logged in with entity id 93 at (448.64588595464755, 64.0, 177.56978889094464)
[07:20:25] [Server thread/INFO]: Kumasasa joined the game
[07:20:28] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 2539ms behind, skipping 50 tick(s)
[07:20:55] [Server thread/INFO]: [Kumasasa: Title command successfully executed]
[07:20:55] [Server thread/INFO]: Kumasasa lost connection: TextComponent{text='Disconnected', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}
[07:20:55] [Server thread/INFO]: Kumasasa left the game
[07:21:39] [User Authenticator #2/INFO]: UUID of player Kumasasa is 212c6adb-6aad-4b04-ab21-0d52a98931c0
[07:21:39] [Server thread/INFO]: Kumasasa[/127.0.0.1:60413] logged in with entity id 2685 at (448.64588595464755, 64.0, 177.56978889094464)
[07:21:39] [Server thread/INFO]: Kumasasa joined the game
[07:23:03] [Server thread/INFO]: Kumasasa lost connection: TextComponent{text='Disconnected', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}
[07:23:03] [Server thread/INFO]: Kumasasa left the game
[07:24:24] [Server thread/INFO]: Stopping the server
[07:24:24] [Server thread/INFO]: Stopping server
[07:24:24] [Server thread/INFO]: Saving players
[07:24:24] [Server thread/INFO]: Saving worlds
[07:24:24] [Server thread/INFO]: Saving chunks for level 'Molokai'/Overworld
[07:24:24] [Server thread/INFO]: Saving chunks for level 'Molokai'/Nether
[07:24:24] [Server thread/INFO]: Saving chunks for level 'Molokai'/The EndSingleplayer
15w36c
19:54:01] [Server thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shield
[19:54:01] [Server thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shield
[19:54:01] [Server thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shield
[19:54:01] [Server thread/WARN]: Unable to resolve BlockEntity for ItemInstance: minecraft:shield
java.lang.NullPointerException
at ux.a(SourceFile:401)
at uz.a(SourceFile:213)
at ayk.a(SourceFile:50)
at ll.b(SourceFile:153)
at bvd.a(SourceFile:98)
at bvd.j(SourceFile:130)
at net.minecraft.server.MinecraftServer.run(SourceFile:427)
at java.lang.Thread.run(Thread.java:745)
[19:54:01] [Server thread/INFO]: Preparing start region for level 0
[19:54:02] [Server thread/INFO]: Preparing spawn area: 26%
[19:54:03] [Server thread/INFO]: Changing view distance to 12, from 10
Can confirm for 15w36d