I just received a notification that Firefox 5 is available.
There were a couple of issues when I upgraded to Firefox 4, such as a couple of plugins that were not supported and stopped working, and a new layout that took some getting used to.
This time around I am going to wait a while before updating, just to see if there are any bugs.
If anybody else has updated to Firefox 5, please post here and let the rest of us know if it is worth updating or if it would be better to wait.
All the best,