Thanks for these reminders. You see the extension widget in the bottom of Firefox on my screenshot, because I'm using Firefox 4, in which there is no more statusbar. The statusbar has been replaced by an add-ons bar, which means you can drag any toolbar extension widget to it. I have included a code to auto-add the widget to the main toolbar as you described, but you can move it around by right-clicking on the toolbar and selecting the the "customize" option.

I'm already working on the next version, which will have some context menu options. For instance, while reading a question in the site it will be possible to right-click on the page and set that question to be ignored, so it won't show in the extension menus and won't trigger alerts when updated. Next version will also fully support meta.askubuntu and the user will be able to easily switch between meta and askubuntu

I agree. It could have a little transparency, to keep the color.

Looks like if you enter a captcha and it is accepted, next time you try to validate another post with the same captcha it fails, but the system doesn't show a different captcha by default. Is that normal?