Gorge Tunnels allow the update's namesake character to create fast passages across maps. Descent is a brand new battlefield, and the most visually rich map yet seen in NS2. Exosuit's may now attach Railguns, capable of disintegrating aliens in explosions of xeno-goop.
The Insight Spectator System has been revamped to significantly improve viewer experiences during eSport events such as the NSL Invitational Cup. And, the Spark Engine now supports First Person Spectating.
Gorge's can now spawn Babbler's - Viscious little minions that become your personal army. You can direct them to attack enemies, attach to friends (granting them protection from marine fire), or just follow you about like mini alien bodyguards.
Graphics have been improved - Spark can now render the blood splatter, bullet holes and reflections that really let you know your team is getting slaughtered. Every existing map has been updated and enhanced for better balance and flow of play.
A new tutorial system provides contextual help to new players every time they get their head bitten off or hide riddled with bullets.
Gorgeous features a myriad of smaller changes that contribute to improve the game overall. From weapon balance tweaks, to new cloaking mechanics, to a slew of bug and stability fixes, a huge amount of work has gone into taking the NS2 experience to the next level.
All of this is free of charge to anyone that owns a copy of NS2.