Can someone describe some of the new features to me, if it is already known how they work?

well i think in this game you are able to make your own video clip to music of your choice and the clip is you doing your tricks around town. i also think that if you choose to do sometthing other than something else your path will be different to what would of happened if you chose the something else. if you get what i mean. hope i didnt confuse you even further. but this is meant to be a really good game.

it is a lot more freedom you can choose 3 different skating paths.
Freedom to Play Your Way: Players are now given unprecedented control of their skating experience. They can mold and shape their character however they choose – the choices they make and the paths they travel determine how they evolve as a skater. As gamers progress, they develop into any combination of three skater classes, acquiring attributes and skills of a contest-winning Career Athlete, a fast and furious Hardcore Skater or a creative maverick Rigger, who alters and modifies the world as a giant skatepark.
Create Epic Skate Videos with the Full-Featured Video Editor: Players can capture all of their sickest tricks and bails with Neversoft’s new video editor to make their very own skate videos. Command the footage using a full-suite of video editing tools, lens modes, camera angles and effects to cut clips and combine clips, add a personal soundtrack and even showcase online to share with others or simply move up the leaderboard rankings.
Seamless Integration Between Online Multiplayer and Single Player Experience: Gamers can join online multiplayer action anytime directly from the single player story mode and take all of their character’s skills, attributes and stats online. Additionally, they can create their own personal Skate Lounge and invite others to view their winnings or join them for an online skate session.
Expanded Gameplay Mechanics Deliver Unprecedented Control: Tony Hawk’s Proving Ground introduces eight all new gameplay mechanics empowering players to play the way they want: Expanded Nail-the-Trick™ moves such as Nail-the-Grab and Nail-the Manual, Bowl Carving, Aggro Push, Skate Checking, Climbing/Exploration, Environment Altering and Rig-a-Kit.
Guidance From Skateboarding Pros to Create Your Legacy: As they define their character, players will learn new tricks and mechanics from their favorite skateboarding stars. Tony Hawk’s Proving Ground features a diverse roster of the sport’s hottest athletes, including Tony Hawk, Ryan Sheckler, Arto Saari, Jereme Rogers, Daewon Song, Jeff King and more.
Greater Variety of Customization: At any time they want, players have the ability to use the Rig-a-Kit and Environment Altering mechanics to transform any locale into their own personal skate park. They can even personalize their Skate Lounge with items such as furniture, plasma TV’s and more. Tony Hawk’s Proving Ground also delivers a full, ambient world from real-time weather effects to random world events for the most empowered and dynamic experience ever.
courtisy of Gamestop.com
http://www.gamestop.com/product.asp?product_id=281768