In OS X Lion, there is an option to restore windows upon restart. However, I never used it. Yet, every time I went to shut down my Mac, I was prompted to shut down with the option, “Reopen windows when logging back in” pre-checked. And I would uncheck it every night. Now, as of 10.7.4, I noticed that the dialog box does not pre-check that option for me. I have not tested if Lion actually now remembers your preference (which would be nice) or if they just changed the default. Either way, I am happy.