Ah, the joys of cross-platform development....
Several bug fixes have landed to fix a few issues found on Mac OS X and Linux. The fixes were tested on Mac OS X 10.5.1 ("Leopard") and Ubuntu 8.04 ("Hardy Heron"). For the latter, testing was performed using Gnome 2.22.1 and KDE 4.
The bug fixes, summarized below, will be included in the next beta release.
Mac OS X fixes
The extension preferences dialog (in Firefox, Tools → Add-ons, select Panic Button then click Preferences) is no longer blank (this was bug 19025).
The Restore Session toolbar is now working. Previously, the floating toolbar couldn't be moved properly, and clicking on it didn't do anything (bug 19026).
Firefox will really quit if Quit is set as the Panic Button action. And if Hide All Windows is the Panic Button action, Firefox will really quit if you clicked Exit on the Restore Session toolbar. Previously, all application windows would close, but you would still have to manually quit Firefox by choosing Firefox → Quit Firefox or pressing Command+Q (bug 19027).
The shortcut key to invoke the Panic Button action on the Mac is now Command+F9. The F9 key as used on Windows and Linux conflicts with Exposé (bug 19024).
The extension preferences dialog only had a Close button; there was no way to apply changes to settings (bug 19051). This has been fixed so that it now has OK and Cancel buttons.