Summary
Great Expansion for Jedi Knight.
The Good
My biggest complaint about "Jedi Knight" was the lack of seedy, underworld missions and commando-type operations. Playing Mara Jade, you get to go back into the dark belly of the underworld of Star Wars.
In addition, MOTS introduced tons of fun new items and enemies, including the fearsome battle with a Rancor itself, complete with the proper music playing at the proper times.
Other operations opened up new elements of the Star Wars universe. Kyle Katarn's early mission into the Imperial Asteroid Ships was certainly original, and Mara Jade's journey through the Sith Temple is downright creepy.
MOTS also included some graphical enhancements like multi-colored lighting.
The Bad
Mysterious of the Sith was *very* hard. I don't count that necessarily as a fault, but some people might.
Damaging Kyle Katarn's character wasn't very good, and neither was the ending (didn't Yoda say that once you start down the dark path, forever will it dominate your destiny?).
Finally, the cinematics in this game were miserable. Although the engine can cut the gameplay okay, the cinematics were terrible compared to the real-life FMV from "Jedi Knight". True, they got away with a lot more in this one (such as Mara Jade crashing through the skylight), but that's not much of a justification for the "Wing Commander" crowd like myself.
The Bottom Line
An excellent expansion brought to us from the same people who created the *excellent* "Outlaws: Fistful of Missions" for "Outlaws". Highly recommended to any aspiring Jedi.