Saboteur hasn't really found its niche in competetive play. But turning over hits into crits is "a good thing"™
Saboteur, for the people who don't have the card nearby and have forgotten what it does is:

It doesn't cost the world. There's a good chance it'll trigger once a ship is damaged. It doesn't offer the target any way to get out of it.
Put it on a low PS ship, cosy up to a large butted bastard and go to town. With any luck you'll trigger something to hamper your victim even during activation.
Saboteur, because the best thing in life is making your enemy suffer.