With proper micro, they will annihilate any infantry they come across. It requires a lot of kiting to pull it of though. They are pretty fast as well, so they are a good first drop-in unit to capture extra reinforcement points.
I tend to find them more useful in defensive situations, as their speed and infantry annihilation skills allow them to stop the enemy from capturing RPs and in time even rob them of their starting RP. Having an Infiltrator Academy is very handy in a defensive battle, as their Anti-Vehicle grenade can also pretty well smash everything (but often at the cost of the Infiltrator).