As well as the information panel, you can also bring up contextual menus within other panels. For example, when viewing the DOM of the page in the HTML panel, you can right-click on any element or attribute, to look it up in the reference search, or view a code example for it.
I know James is keen to hear any feedback on Firescope (feel free to add comments on this blog post if you want - I’ll be sure to pass them on).
The extension is in the mozilla add-ons directory which is the best place to download it (because then it will subscribe to updates). However, you’ll need a Mozilla login to get it from there because it’s still in the sandbox (in other words, not quite yet approved for mass public distribution). Alternatively, you can download and install it directly from the page on sitepoint.com (but without the auto-updates facility).
As well as having a new reference tool within Firefox/Firebug, the online reference has, itself, also had a make-over which gives it just that extra bit of polish. So even if you don’t feel like installing the tool, you can still check out the reference for yourself.