So everything I read currently convinces me that SWTOR is totally geared up for the alt-lovers among us.
Tal has held forth expressively on his frustrations with the ease of acquiring experience and skimming through planets with grey quests. But all the recently-released legacy information increases the impression that we're being encouraged to roll our way through multiple classes, visit some planets in depth on different characters, and each time finding more to explore. Bring it on.
Of course, it is irritating if you are a completist by nature, and want to have one character who has done everything. And it's maddening if you can barely find enough time to play one character, let alone more... *cough* However I do find myself more inclined to play alts here than I have elsewhere (but I will understand collective scepticism until you actually find me levelling anyone properly).
I'm glad to see that they are also looking at freeing up some of the limitations of cross-faction chat - this would make a big improvement to the joy of alting.
The individuality of the story plots aren't enough to pull us through however. So I guess that's a good reason that the different planets can flood us with quests and experience. I'm already guilty of rapid spacing through quest dialogue (I knew I would be), but I have several planetary questlines and heroic/bonus lines of which I've just touched the periphery and would like to know more.
I think Bioware have crafted a game to reinforce subtly that culture of alts-rolling, but I guess we'll have to wait for the next big patch to see how that plays out in the community.