One of the reasons firefox appears to be slow is the checks it does for bogus websites, on startup it does a self check and checks for updates for itself and any other features you have installed.

Once the initial checks are done the only checks after that are for harmful sites etc.

The way to make firefox run quicker is to stop it checking itself for updates and addon updates, if anyone can run the code and strip it down then let the community have the end result, would be much helpful and appreciated.