1. Action-Oriented Combat: The first new element is apparent within your first five minutes of playing the game. Tabula Rasa 'feels' like a first-person shooter, complete with crosshairs. It's very visceral: you don't select an enemy and then press an attack button to start your attack cycle. You simply point your weapon at a bad guy and start blasting away! There's plenty of RPG-stats working behind the scenes (your skill with the weapon determines if you hit, your weapon stats and skill bonuses determine damage, etc.), but during gameplay you're definitely focused on the action. Tabula Rasa does a great job of keeping all of the relevant info right there on the playfield, so you're not staring down at your skill bar all the time.
Related to this first point is the fact that the game is focused on tactics and position much more than other online roleplaying games. For example: you'll actually need to use cover. You'll find yourself dashing between sandbag bunkers or planning your assaults around shelter. Crouching behind a low wall makes a huge difference on the outcome of a battle. Furthermore, teamwork is encouraged through battlefield situations. For example, a Bane drone might be invincible from the front, so some players will need to distract it while fellow players flank it for the kill. Or an enemy might be projecting a shield around fellow enemies, so someone with good melee skills will need to run in to take out the shield generator up close in order for the other characters to open fire. Tabula Rasa has a very different feel than the "Tank / healer / damage-dealer" class structure you see in other games.
2. Branching Characters: As Producer Starr Long told GameSpy: "Tabula Rasa is the first MMORPG with a save-game system." Most online RPGs front-load all of your big character decisions into the character creation process, and you're stuck with the class you picked before you knew anything about the game. Tabula Rasa changes it up. Your initial character is just a recruit, like all the others -- after playing the game, you decide how you want to specialize as you begin exploring a branching set of character options. Other games have done this before, but here's what's new: you can "Clone" your character at any time, meaning you can always go back to an earlier version of yourself and then start leveling up your character in a completely different way. This is a much more player-friendly approach and I wouldn't be surprised if variants of this become the norm.
3. Dynamic Battlefields: Other games have similar systems, but it's such an integral part of the Tabula Rasa experience that it bears mentioning here. The environment in Tabula Rasa isn't fixed; strongholds will change hands dynamically. Even if nobody is around, the Bane or the Allies will launch periodic assaults. It's not unusual to be running to a location only to stumble on a massive firefight. You might pick up a mission at a base, then return an hour later to find it overrun with enemy troops. If you can fight them off and recapture the base, you'll be able to turn in your mission. Some of the rarest items in the game will only be available by completing quests given by NPCs who won't be there unless you take over and hold massive enemy strongholds. The world really is dynamic, and it shapes the way you play the game.
There's a fourth element that may separate Tabula Rasa from the pack, and while it's not a new idea it's fundamental to a great game. That's the color and texture added by the stories and mission design. Garriott has invented a whole alien language, called Logos, that's littered throughout the game world. Study the alien symbols long enough and you (personally) can become fluent in the language, picking up game hints or discovering new things in the game.
The world is also peppered with ethical dilemmas that don't have clear right or wrong answers. For instance, you may investigate who's stealing supplies from your home base, only to discover that the troops on your most beleaguered outpost are skimming a little off the top just to stay alive in one of the toughest areas. Do you turn them in or look the other way? In another area the vicious Bane are about to get a strategic toe-hold in an area, but you can stop them by blowing up a dam. Do you take the opportunity for a guaranteed military win, or do you risk the operation in order to evacuate the innocent people in the valley below? No choice is right or wrong, but each opens up different paths through the game.
