Development
Development of the PC and Console version of the game split close to PC launch
There were radical changes to the code in order for the game to translate properly to Console
Battle.net had to be completely ripped out of the game and replaced with Xbox Live and PSN integrations
The first pass for the Console translation was implementing everything that existed in Diablo 3 on day 1. Since then the team has been hard at work making Diablo 3 a good Console game. All the PC patches were implemented over time
Diablo 3 runs at full 60 FPS during most of the game. The exception being when, for example, "4 Witch Doctors all play Zombie Dog builds and constantly explode them"
Gameplay
Crafted items now tailor their stats more to the class that has crafted them. Developers feel this is one of the more important changes coming to Consoles
White and Blue items drop far less
Artisan upgrades cost less gold
Vendors are much more likely to sell Rare gear
Class items are far more likely to drop for the class being played
Some monsters have had their health and damage adjusted for Console. For example the Withermoth's damage has been increased by 500%, as you only get to meet a few of them during the entire game
Itemization
The itemization changes on Console are not what we're going to see in the future itemization patch. Instead they've been what the Console team came up with to streamline the flow of items
The 5-6 fansite attendees at Blizzard HQ managed to find a total of 3-4 items Legendary items on Act 1 Nightmare in one hour
Offline
Initially the Console version was also supposed to be online-only, but Blizzard's research showed a huge part of the Console population didn't have an Internet connection
There are anti-dupe mechanisms in place, but Blizzard knows they'll eventually be overcome
There are some concerns about Trading in the Console version, because of the lack of Auction House
Interface
Not a single part of the PC interface was kept. All is changed
When looting items icons appear that compare the loot you got to what you have equipped. Instead of showing the full numbers like the PC version, the Console icons simply point out if the item is better or not in terms of Life/DPS/Protection
You can still view a full comparison between the items in your inventory, where all stats are compared
Coop
When you play with a friend on the same screen if you move too far away from your coop partner you'll yank him towards yourself in a pretty intuitive manner. This helps a lot with AFK players
You can play on a single screen or online with up to 3 other players and also do a combination of both