How does the party system work in Star Wars: The Old Republic?

Question

From what I've read and seen in clips and developer commentary, it looks like you actually level up/equip/control more then your main character?

So is it possible to play the game without ever having to party with other people?

Answer 1

There will be single player content, yes.

Answer 2

It may be possible to play through the game without ever having to party, BUT you'll probably miss out on a ton of content.

From what they've announced, there's nothing to indicate that you'll be able to equip / level up / control other characters outside your main.

In fact, one of the big things they're proud of about this game is the fact that you'll be able to play an RPG in an MMO setting with a full blown story on the level of single player games.