Just a quick reminder (I guess, most of you thought of this anyway, but one can never be too careful): If you packed your weapons in the arms, you might end up with free slots. Make sure you clicked the checkboxes for Lower Arm Actuator and possibly Hand Actuator. That gives you up to two more internals per arm, which CAN be destoyed, before they destroy something useful, like... let's say: Your PPC. Since free space isn't hit by a crit, they can only hit, what's there. So let them hit something you don't really need. If I just helped ONE of you, it was worth mentioning
Are you sure actuators can be destroyed in MWO? I know TT allows you to crit actuators, but that results in penalties. IF an actuator can be targeted by crits in MWO, I would expect that A) The actuator stops working, restricting the movement of you arms B) Bitching Betty would tell you that it was destroyed similar to weapons, equipments, and ammunition. If you have a source that confirms actuators can be crit in MWO, please don't hesitate to link it.
That having said, if you have the extra crit slot, it is not a bad idea to activate them. Nothing bad come out of it I guess.
Unless it is the Stormcrow Prime. Do you really want those nasty/creepy "stranglers" hands on your mech?