Please make a Full backup Copy of your Firefox 2 installation NOW

Please make a full backup copy of your Firefox 2 installation.
Edit:I.E. Do not upgrade your One and Only copy of your Perfectly Configured FF2P
You know, the one you spent hundreds of hours tweaking and perfecting

Many things may get screwed up by the upgrade to FF3 that are beyond our control.
I'm thinking here of Add-ons/extensions that won't work properly till they are updated.

If you find that you have Add-ons that are not ready for FF3 they will be disabled.
If you later get updated versions will they be able to migrate your myriad of settings and preferences from the disabled versions or will they install from scratch, I don't know.
Think of those non-canonical tweaks you've made to the original, have you written them down?

If you keep a working copy of FF2 you could update the Add-Ons there and than upgrade to FF3.

It is best to check Now, before you upgrade to FF3, to see if there are newer versions of your Add-Ons already.

Summary:
Update Add-Ons/extensions, Plugins, themes, etc now, Before upgrading.
Keep a Full copy of FFP2 around for a while, just to be ready if you need it.

You have been warned

Tim