I don't know about the purchased abilities, but the base abilities are sniping, (1 shot kill humanoid targets) and mind control that links something to her but you can control both specifically. I'm sure the bonus abilities are just as cool
I've used spectres. I like them. I don't want to get ghosts and regret it. And the spectre attack ability does not decloak you. I've used it religiously and not had the problem of suddenly getting smacked upside the face.
Both the ghost and the spectre can have infinite cloak once upgraded. In my opinion the spectre is far supperior. *SPOILER* and incase anyone is wondering, Nova lies Spectre's do not become psycopathic killers.
"Emancipate yourself from mental slavery none but ourselves can free our mind"