With WP 3.3, the shortlink feature from the admin bar is gone. There is no way to access wp-bitly shortlink now except for going into the edit post section. It would be great if you can add Shortlink tab back to the admin bar.
I am sure a lot of users would love it. You can also make it like an option that people can check on/off (this will allow users who don't want it to turn it off).