Noticed over on The Burning Edge that the latest Deer Park (aka Firefox 1.1) nightly build has some interesting new fixes/changes added;
Fixed: 216466 – Use error pages instead of dialogs for e.g. HTTP networking errors (default browser.xul.error_pages.enabled to true).
Fixed: 298293 – Turn on fastback/bcfache by default in ff 1.1a2 / gecko 1.8b3. (default browser.sessionhistory.max_viewers to 3.)
Fixed: 296850 – Frame injection spoofing with targets (bug 246448 returns – SA15601).
Fixed: Several other security holes.
Fixed: 76831 – [Windows] Slow to restore from minimized state (default config.trim_on_minimize to false).
Fixed: 176079 – Popup blocking does not stop Flash from opening windows.
Be sure to read the page itself for other fixes/bugs & download links if you’re feeling experimental. A lot of the preference changes are covered in our Firefox Guide already.