One of the earliest episodes where the show begins to show what it will ultimately be capable of. The insertion of the Sherlock Holmes theme appeals to me, so be warned if you dont like that yourself. It is also another holodeck episode which allows for the location of 19th/20th turn of the century setting - which I personally also liked.
The introduction of Moriaty is what will become the start of at least one other special episode, which I also found entertaining. The plot is simple enough as Jordi's lack of thought in his instructions creates the ultimate adversary for Data in the form of a sentient holodeck character. Though the fight between the two is no more than a tussle at best, there is always the threat that Moriaty could destroy the Enterprise if he ever learns how to fully control the computer.
Though nothing truly important happens, we get the creation of a thread subplot and more character development from this episode and Dr. Pulaski's character develops a soft edge to her hardened exterior.
Not a necessary watch unless you love any of the following themes: Holodeck, Sherlock Holmes, Moriarty.