The most obvious is the new Reading List. There’s a pair of glasses to the left of the Bookmarks icon, under the Back button. Have you ever landed on a webpage, didn’t have time to read it, but didn’t want to add a bookmark for it? Now you can click on the glasses, and then on the Add Page button. Now you have a Reading List to browse when you have time, and when you’re done with the page you can just click the little X that appears when you hold your cursor over the link
Another new option is Resume. Look in the Preferences (Safari>Preferences>General), and then at “Safari Opens With”. You can set Safari to automatically open up with all the windows from your last session.
My favorite change is Drag-and-drop Downloads. You can now drag items out of the Downloads window in Safari, so you can easily move downloaded files wherever you want them to go, without having to view the Downloads folder first.