Google has graduated three popular Gmail Labs tools to proper Gmail features: reply to all, quote selected text and, the most useful of the bunch, the "Send and Archive" button.
Unlike some new features for Google Apps, these are available right now in Gmail, though all three remain off by default.
To enable the popular "Send and Archive," which turns the Send button into a dual-function button that sends your reply and then archives the conversation, head to settings and look for the new "Show 'Send & Archive' button in reply" option. While you're in Gmail's settings you can also change the default reply mode to reply all, though frankly that seems like asking for trouble.
The quote selected text feature is not a setting, it's just the new behavior for replying to messages. Select a block of text in an e-mail, click reply and only the selected text will be included in your reply.
