After i downloaded the new iOS 5 for my iPhone 4 safari isn't any different?
There are some under-the-hood improvements to performance, and also some changes to the settings (such as a private browsing option), but there aren't any major changes to the Mobile Safari interface on the iPhone. The iPad version now has tabbed browsing instead of the window-switcher, but the iPhone is too small for such a thing to work.

The two features you may notice are Reading List and Reader. Reading List is essentially a  bookmarks folder that can sync with desktop Safari. You can add items to it from the Share item (centre button on the bottom toolbar). Reader will reformat some webpages (long articles) to make them more readable, removing ads and menus so that you've just got the text. You can access it from the grey Reader button in the address bar once the site loads (note that it's not available on all sites, just those that Safari can competently reformat).