It's interesting to note how each season finale of Justified has, in a way, defined the show to itself. They've gotten progressively less violent and more melancholy (as the episodes' titles got progressively more ominous): Season 1's "Bulletsville" featured a climactic shootout. Season 2's "Bloody Harlan" had a bit of gunplay but eventually ended with a quiet scene between Mags and Raylan. Season 3's "Slaughterhouse" culminated in a short, talky standoff between Quarles, Raylan, and Limehouse. Season 4 continues this trend: it's the quietest finale that Justified's ever done. It's a fitting end to a season that bucked the guest-star-villain trend of the previous seasons and mostly succeeded in branching out the show from the lighthearted action show it sometimes gets labeled as.
Though at times it feels a bit too neat and tidy, "Ghosts" wraps up the season satisfactorily (unlike a certain zombie show I could mention). It brings the various threads to a close that nicely with the other seasons, while opening things up for the story to continue. The episode is mostly focused on the two last lingering plot threads: Boyd and Ava dealing with the aftermath of Ellen May's confession and possible police investigation of Ava's murder of Delroy, and Raylan's ongoing conflict with the Detroit mob. It's a strangely paced yet meticulous episode, and one that defines what Justified ultimately wants to be: a show about people damaged by their past, where the gunfights and car chases are incidental.
One little spoiler I will give you: "You'll Never Leave Harlan Alive", the song that ended both Seasons 1 and 2 and was left out of Season 3 to the chagrin of fans, makes a triumphant — if understated — return.