The first three levels of this game were released as the demo game Ambush At Altyr 5 that could be played without the base game Star Wars: Jedi Knight - Dark Forces II.
In the German gaming magazine PC Player (issue 01/1999) Star Wars: Jedi Knight - Mysteries of the Sith received a special award as "Best Add-On in 1998".
The cinematics are all pre-rendered and on a computer with a good 3D videocard, they can look a lot less detailed than the gameplay.
In one of the mid-levels of the game, you can find a small personal collection of "artifacts" a crime boss has been collecting. Among the items there is a Dark Trooper's helmet from "Dark Forces".
There's a very cool secret level included in the game, to access it follow the instructions at lucasarts own page:
In the level you play Luke as he comes to Rescue Han and Leia from Bespin's Cloud city on ESB. Check it out! you get to fight against Boba Fett, Dark Kyle and Mara (though no Darth Vader, bummer).