GameSpot posted an interview with Game Director James Ohlen about companions in Star Wars: The Old Republic. Mr. Ohlen revealed that companions will function similar to other classes in the game, leveling up alongside the player and unlocking skills as they progress. He also talks about a new system that will allow players to set up companion behaviors (AI) in combat beforehand, managing which abilities they do and do not use.
Along with the James Ohlen interview comes a Developer Dispatch video on companions featuring Lead Writer Daniel Erickson, Principle Lead Combat Designer Georg Zoeller and Art Director Jeff Dobson.  The developers talk about hitting the cornerstones of Star Wars with companions such as droids and aliens, how companions level-up and unlock new abilities just like players and the affection system, where gifts can be given to companions opening up new conversations and quests.
Update @ 3:39PM EST: BioWare also released a Developers Blog on Companion Characters – Part 1
