If it has memory seats it's the luxury package. If not it's the premium package.I bought a new 2011 IS250 RWD last October. Tungsten Pearl with the black leather/dark grey maple interior. I'm not sure exactly what package it was, but it came with heated/ventilated seats and Navigation among other things.
Nav is a standalone option, not related to any packages.... only "option" relevant to Nav is if it also has Mark Levinson or not. (it'd say Mark Levinson on the head unit)
Good thing too, since there really aren't anyNo plans for any performance upgrades
and I agree with you 100% on the seats in the F-sport model... the side bolsters are nice, but not give-up-vented-seats nice.