Ahoy! The following are changes from Vanilla are present on these high seas:

• Iron Golems do not drop iron
• Villagers will not give emeralds
• Podzol will form from moss
• After creating a nether portal and passing through, a portal is not created in the nether
• Lava cannot be picked up in the nether with a bucket
• Each island's spawn limit is 50 for hostile mobs and 100 for passive mobs
• You are only allowed 1 miner minion and 1 fisher minion to be placed at once

ARR, don't be a landlubber!  If ye come across other murky waters, shout 'em from ye lung below.  This pirate will add it to his bounty in this post.

Podzol will 'not' form from moss, typo
Rooted Dirt will also not form from moss.
You also cant dupe dirt with the coarse dirt recipe
You can craft Coral Blocks by combining 9 of the corresponding fan

Mob caps are also subject to change btw if a reason ever comes about, No one has ever hit a mob cap yet though.
Bat and Phantom mob limits are 0 (Phantom membranes drop from Pirates and during double drop event from all mobs)
There's also a 50 hopper limit for lag.

And minions aren't in vanilla ;p