I have also tried the RankQuest Firefox extension. This extension can be downloaded from https://addons.mozilla.org/firefox/1471/. This extension adds a toolbar to Firefox. The toolbar contains links to many SEO-related functionalities, including the information on query terms and specific sites.
Below is a screenshot of what the extension looks like:
Below is the score for each category:
Ease of installation: 5
Ease of use: 2
Amount of time for the information to appear: 5
Usefulness of information presented: 4
Amount of real estate taken up: 3
Ease of installation: Installation was quick and problem free.
Ease of use: Clicking on the toolbar takes you to a new tab. After checking several sites / query terms, the number of tabs can become unmanageable.
Amount of time for the information to appear: Data loads quickly.
Usefulness of information presented: Good information on the specific sites / query terms requested. There are also links to general SEO help. I don’t believe this is a useful feature for any SEO serious enough to install a toolbar.
Amount of real estate taken up: An additional toolbar is shown.
Documentation: Adequate documentation is available at http://www.rankquest.com/toolbarhelp.html.
Ability to provide the option within the tool to specify whether to open a new tab or use the current tab.