...and if you thought "Military Intelligence" was an oxymoron, whooo boy...
Sith Intelligence is probably not as effective as Imperial Intelligence was. Say what you will about Darth Jadus (...but not right now, only so many hours in the day), but it was a clear pattern throughout the Agent storyline: The more the Sith get involved with spycraft, the worse it gets for the Empire, for the people on the ground, for civilians, really for anyone within saberin' distance.
Still, it'd likely also attract Sith that are interested in that sort of work, and they'd be better equipped to not just torture anything that gives them lip. Probably better able to manage the tangles of Sith politics and avoid all of their operations from getting ruined by Darth Stabbiwonkers types.
But there's a reason why the Republic was able to, at one point, get a sleeper agent into the organization and have him progress to being the Sith Intelligence's Minister's right hand man. Granted, Lana was more of an operations manager than a spy, but if that was the top brass at the time, and she quit, one only wonders how capable her replacement is...