Fluffingly, Adeptus Mechanicus - as described in the mission and flavor text - works like you expect. They're cold, inhuman, but still very much conflicted about their duties, tasks, and people disagreeing with them. Mechanically, their biggest weirdness comes in Doctrina Imperatives and Canticles of Omnissiah, global abilities that affect either the more human or the more borgy parts of the army. The boosts are welcome, but the distinction isn't always easy to remember.
