I did the incremental update of 5.0 MB from 2.4.1. A few add-ons were not compatible, but will become compatible, thanks to the neat Add-on Compatibility Reporter.
As you can see from my User Agent, it is based on Firefox 8.0.1.
UserAgent: Mozilla/5.0 (Windows NT 5.1; rv:8.0.1) Gecko/20111121 Firefox/8.0.1 SeaMonkey/2.5
