ConceivablyTech has an overview of some of the major new features of Firefox 5. It includes social sharing features, new tab features, a file upload indicator, a Home app tab instead of a home button, a built-in PDF viewer, taskbar web apps, identity management and more.
9. The sharing features appears to be the big deal in Firefox 5 – there will be a new paper plane logo in the URL bar that provides access to your social media accounts, such as Facebook, Twitter and we assume other services such as Reddit, Digg or StumbleUpon as well. You can add social accounts and “share” websites directly from your URL bar. there is no need for clicking a “Like” button.