When first introduced, users had the ability to turn the Admin Bar on and off from their user profiles
Many WordPress users complained that it duplicated functionality and stole screen real-estate and this was quickly followed by a stream of plugins and code snippets that disabled the Admin Bar completely.
As of WordPress 3.3 the Admin Toolbar has replaced the Admin Bar and has become a permanent feature.
Users can now optionally switch it off while in the front end of the website but it is always present in the Dashboard, replacing the header area of previous WordPress versions.
The Toolbar can of course be customised for your needs by removing default menus and adding your own.
Some in the WordPress user community still express concern that it duplicates functionality from an already streamlined Dashboard, but it’s here to stay and make good use of it we should.
If you are using WordPress as a Content Management System for your client website projects, you will likely want to remove some of the default Toolbar menus and entries such as the links to wordPress.com web pages.
For those who don’t enjoy (or can’t be bothered) coding, there are plugins such as Custom Admin Bar that make it easy to quickly customise the Toolbar to your needs. It also works with WP Multisite.
If you’re looking for better control over the exact look and feel of the Admin Bar then you’ll have to create call-back functions in your functions.php file, specifying the areas to customise.