I only played on Republic so far. Performance went like this: Tython was meh, Coruscant was bad, Taris was horrendous, Nar Shadda was meh, Tatooine was horrendous and now Alderaan... i cannot advance cause it lags more then what i can put up with.
I think my system is pretty average, more than enough to run this game. The only thing i lack is ram. Only 2 gigs. I will upgrade it to 8gigs and see what happens. If that doesn't fix it then i'll have to give up on this game until a major performance patch drops in.
Just wanted to let off some steam. Buhbai.
EDIT: "More than enough" calculated by reading the system requirements and doing a test on SRL.