The first beta version of Opera 11 is out today, and as expected, it brings a very important yet long-overdue new feature to the mix: extensions support. The latest pre-release version of the browser uses a similar approach to that employed by other WebKit-powered browsers like Chrome and Safari, installing extensions as buttons to the right of the search bar that can auto-update. So far there are a little over 130 extensions in Opera’s extension gallery -- a small number compared to Firefox or even Chrome, but the feature has been available only in a limited alpha release for the past month.

Opera 11 also comes with another major feature called tab stacking that will come in handy to those who have large numbers of tabs open on a regular basis. Basically, instead of keeping tabs alongside each other, tab stacking enables you to group them by site or theme, similar to what Panorama does in Firefox 4. To use it, simply drag one tab on top of another, after which you’ll see a small arrow next the tab that will let you expand or contract groups as needed.

Mouse gestures have undergone an upgrade in Opera 11, with a new visual interface highlighting available mouse paths, the address field now hides unnecessary information and puts the security status of each page front and center, plug-ins like Flash can be set to load on-demand, and browsing speed gets a small boost. You can download the latest version of Opera 11 Beta for Mac OS X and Windows – Linux users will have to wait a little longer or get the alpha here.