Adding Widgets should be done through a dialog. Adding Widgets should be accomplished through a dialog window similar to how add-ons can be added in Firefox. This gives a very connected feeling to the browser and the Widgets just as skins (themes) are currently implemented.
The Manage Widget window is uber boring. Sure there aren’t a lot of things that you need to do when managing your widgets, but the with all of the space available in the Widgets tab there should be a preview image of the widget along with version information and a good description.
Opera should check for Widget updates automatically. As you may know, Firefox automatically checks for updates to your add-ons allowing you to easily keep up with the latest, most secure and compatible versions. Even a “Find updates” button would be ideal over the complete lack of ability for Opera to find updates for the end users on it’s own.