Just a few things I would like to say about my time as an infiltrator:
I just picked up melee booster implant. I LOVE THAT THING. I love going around gutting all the poor enemies. Knife kills are so fun.
I got a kind of amusing kill today. I was sneaking up on a TR from behind. In front of him was a TR laid mine. I went up behind him and set of the mine. He died, I took no damage. Killed by his own mine.
Today I sneaked up to a Vanu AMS with lots of people loading up. I took out my knife and killed 5 people in a row then sneaked away clean. No one knew what hit em.
If you haven't tried an infiltrator yet, you definitely should. There is nothing quite like the feeling of knowing you just ended someone else's game and they never knew you existed. Crouching and letting hordes of enemies pass you and not so much as flinch in your direction gives you such a feeling of power. This is definitely the best class IMHO.