That has not changed in Safari 6, but it also does not restore tabs automatically on startup, which is what I think the OP was asking.Safari > History > Reopen All Windows from Last Session (in Safari 5)
I'm not sure if this has changed in Safari 6.
Thanks. I don't like that option because it affects other programs as you have mentioned. I will use the option in history, better than nothing until I find another way or plugin.To do it automatically (in Mountain Lion), you would have to go to System Preferences > General and make sure "Close windows when quitting an application" is unchecked. Keep in mind that this will affect other programs too.