On Monday Mozilla released a new version of Ubiquity, the in-browser command line-like utility. While mostly a "stability" update, the add-on has undergone considerable cosmetic change as well, sporting a new dark plastic look. This look can be changed by anyone as part of a new styling system that uses simple CSS. Presumably, user-designed themes will go into an add-ons site as the product matures.
In addition to its new look, Ubiquity now borrows a few features from Firefox 3's "awesome bar." It remembers some of the commands you've used in the past and will let you hop to them right away when starting a new command. For instance, if you frequently use the integrated Wikipedia look-up, simply typing "w" into Ubiquity will pull it up as one of the top search options.
If you haven't yet tried Ubiquity I'd recommend giving it a spin with this update. It's come a long way since earlier releases and can be genuinely useful if you take the time to learn some of the commands. Future releases will no doubt smooth out that learning curve and make it a little easier for the less tech-savvy to approach. Along those lines, Mozilla is at work on a version that lets you pull it up and pick out menu commands with your mouse, just like a contextual menu.