If you haven’t been following the betas, than this day has been a long time coming. iPox for Firefox 3 was officially released on Mozilla’s Addon site this morning.
The new version, iPox 2, has been re-worked from the ground up in hopes of creating the most compatible theme for Firefox 3.
If you come across a bug, please post it in the bug tracker and I’ll take a look into it. There are more updates to come, but this is a good start.