Following a relatively short beta, Opera has released version 11 of its browser. In addition to visual mouse gestures, performance improvements, and memory issue fixes, the biggest feature additions in the new version are extension support and tab stacking.

Much like Chrome and Safari, installing extensions on Opera adds little automatically updating buttons to the right of the search bar. Opera's extension gallery has just over 200 extensions at the time of writing, a small number compared to the number offered by either Firefox or Chrome, but it's a start. Tab stacking, meanwhile, is a feature that will prove useful to those who find themselves with a large numbers of tabs open on a regular basis. As its name implies, tab stacking enables you to group them by site or theme, similar to what Panorama does in Firefox 4. Stacking tabs is as simple as dragging one tab on top of another. To expand or contract the group, use the small arrow that appears next to the tab. Here's a video of the feature in action:

Opera 11 also has better mouse gestures with a new visual interface that highlights available mouse paths. The address field now hides unnecessary information and puts the security status of each page front and center. You might notice there's an improved auto-update system that makes sure that your Opera, its extensions, and Opera Unite apps are up to date. Last but not least, plug-ins like Flash can be set to load on-demand.

You can download Opera 11.00 directly for Windows, Mac, and Linux. You'll probably also want to check out the changelog for Windows, Mac, as well as Linux and FreeBSD.