this requires Spring Social
working on this now. as it stands, the basic behavior is thus:
if you sign in with facebook it should drop you in the signup form page with all the information except your password filled out, and - once submitted - create a local account for you and sign you in. If you already have specified a password, then it should just log you in with your local account. Either way, facebook should save the majority of the tedium
u can sign in / up with facebook now.