To me? It's ability to move between tabs more easily, to open more tabs than Safari (and in the background, no less), and to configure gestures for various functions. Despite being made by someone other than Apple, Atomic makes better use of the iPad's touch interface than Safari. For instance, the way I use this forum is to search for new posts. I scroll down and open all the threads I'm interested in in another tab. I then swipe back and forth among the tabs, replying where I want or swiping them closed when I'm done. I also like that you can put all your bookmarks on the menu bar, as you can swipe it back and forth if they don't fit the screen. And as been mentioned numerous times, you can set the user-agent to another browser, so you're not sent to the mobile version of a web site that wrongly identifies Safari Mobile for Ipad.