[tfmatt]

For anyone reading this, the user-agent switcher is not something to be over looked. If a drive-by-exploit is written for firefox and you are switched to IE... hey maybe they now try to apply an IE exploit and of course it won't work. Basically it is an extra layer to prevent browser specific exploits from being delivered.

[SAI_Peregrinus]

It's also worth noting that uMatrix can spoof user agents, it doesn't take a second addon. (In the Privacy tab on the settings dashboard).