Priority Inbox and adds in a couple much-needed compose and send options. Priority Inbox gets some buffed-up views and controls to change importance settings, and Gmail can now send a notification upon receipt of an important email, which is incredibly cool. Even better, the compose screen now lets you specify any sending address you've setup in desktop Gmail, which is a slice of pure email heaven for those of us who juggle multiple accounts from one inbox. You can also respond to messages inline now and swap between reply, reply-all, and forward much more easily. Best of all, if you're running Froyo you can hit that QR code and go grab the update right now since Google broke Gmail out into a Market app -- no need to wait for your pokey manufacturer / carrier to roll out Gingerbread. (Then again, if you're still waiting for Froyo you might not be quite as pleased.) Ain't modularity grand?