Installed Firefox 1.0 today. Only intended to clean my profile, but got carried away. Here are the main lines:

• backup & delete profile folder
• download & install Firefox latest (what is the difference between a trunk and a branch?)
• download extensions (from extensionmirror, Clav’s extensions, Mozilla update , Gorgias’ extensions, Texturizer or Extension Room.) I recommend downloading xpi’s one by one and install them offline, so you can check your profile between each install.
• If your favorite extensions does’nt install on FF 1.0 because the xpi says « 0.10 & no more », try bumping extensions (but extensions featured at extensionmirror are already bumped before mirroring).
• More at extensionsmirror: Usefull Links, mini-guide on how to get things working again WITHOUT creating a whole new profile (originally on Mozillazine forum), (closely) related extensions, The Most Requested Extensions & Tab-related Extensions.
• Before despair, invoque Firefox Help.