Welcome back Lazarath
For most of us, it's the same game that we know. Depending on how long you have been away, these would be the main changes:
0. New graphics using the Cry Engine from CryTek (2008).
1. Other planets - there are many new worlds to explore. Attach a Space Thruster to a Quad-Wing and fly straight up to go explore them.
2. Calypso Land Deeds - own a share of Calypso and get 'dividends' weekly. You can buy these on the Auction if you are interested in the 'new' (2011) Calypso revenue share program.
3. Buffs - Many new items have been introduced which provide nice buffs to hunters such as Evade/Dodge, Health increase and Health Regen boosts, Life Steal, Decrease Crit damage from the enemy, Increase Crit Hit chance to enemy, etc.... Items such as Rings, Pills, Pets, new Adjusted/Modified versions of existing Armors, enhancers, etc...
4. Loot 2.0 - You will probably continue to hear about this VU for a while which came out last June. The main changes to gameplay seem to have been that hunters are experiencing a lot more Shrapnel and Animal Oils in their loots in general. Planets other than Calypso are experiencing a side effect from this in the form of items just no longer dropping at all since this VU, but I am hearing that this will be fixed. The other big change which is worth mentioning is that the overall cost of armor protection has been reduced a lot and armor is worth using again, unless you have $500 to spend on an Adjusted Resto Chip, which is still cheaper to use then armor. Another change that was introduced in Loot 2.0 is the 'efficiency' value on weapons as an indicator of how much damage it deals versus the cost to use.
Have fun o/
Legends