1) The Ferengi appear much more war-like than in later encounters. Here, they seem to be more like a cross between slightly demented Klingons and the actual Ferengi we know from DS9. For instance, the Ferengi DaiMon claims that his crew would rather prefer to die than to bear the dishonour of surrendering to the Enterprise-D unconditionally. He also offers Picard the life of his second officer ("as it is Ferengi custom") as a form of reparation.
2) Although he was later established as having been one of Professor Galen's best students, Picard his never even heard of the Tkon Empire until the events of this episoe. Instead, he has to fully rely on Data's konowledge on this subject and is suprised to hear that something like the Tkon had existed.
3) Deanna is able to feel the Ferengi DaiMon's emotions and intents, despite the fact that Betazoids can't read Ferengi minds as it was established in later seasons.
4) In one scene, Beverly calls Picard "Jean" instead of "Jean-Luc".
5) As it was common in early Season 1, Picard is depcited as something of a staunch French patriot who speaks sentimentally of the colours on the French national flag (and also exclaims "Merde!" in another scene).
Considering the number of inconsistencies with later seasons of TNG I have to conclude that this episode (and possibly others from Season 1 too) are set in a slightly different quantum reality.