Yes, it’s fine. If you didn’t checkmark WebRep on restart of Firefox 8 after updating, it will be disabled. Then, if you want WebRep, all you have to do is open Firefox Add-ons and enable it.

What I find odd is in Firefox, Add-ons include extensions, themes, and plugins. However, I was never asked about my plugins. In the one Firefox profile that has another theme, it was disabled and the Firefox 8 theme became default. There are threads on mozillazine about the theme issue.