The dual focal points of the season were the introduction of Carter into the command structure and the challenges faced by Atlantis as it faced the growing Replicator threat. Bringing Carter aboard from SG-1 was an organic and natural maneuver given the nature of Atlantis and the challenges the expedition faced in its fourth season.

But sadly, Carter's new role was not maximized in the best ways possible, and Tapping never quite settled into the role. And few of this season's episodes jump out of the pack. While some episodes, like "Trio," were ambitious, others felt more like rehashes, doing less to advance the Atlantis narrative than one might expect, given how much was going on this season (Teyla's pregnancy, the ongoing Wraith threat, the battle against the Replicators).

One episode that does stand out: "Midway," in which Teal'c makes a visit to Atlantis to help Ronan sort through some issues—and gets swept up in a Wraith attack on the station. The series ends the season on a strong note with the two-parter "The Kindred" and the finale, "The Last Man Standing"—but those episodes can't balance out the unevenness that preceded them.

Extra features on board

Stargate DVD titles generally do an excellent job providing engaging supplemental content, and Stargate Atlantis season four is no exception.

All 19 episodes across the five-disc set feature an audio commentary track, for example. Co-executive producer and writer Martin Gero, director and supervising producer Martin Wood, executive producer Joseph Mallozi and directors Andy Mikita and William Waring carry the lion's share of the heavy lifting on the commentaries; actress Amanda Tapping is the only cast member to weigh in, on the episode "Lifeline." And unlike many bumbling audio tracks, the Stargate crew's commentaries are cogent and offer intriguing insights into the direction, logistics and intention of episodes and story arcs.

The commentaries are well done and even easy to access, presented as they are both under the "Special Features" menu and from within the "Language" menu for each title.

Unfortunately, not all of the extras are superbly presented. In addition to the commentaries, each disc features two sets of galleries—one for still photos and one for production galleries. They're a great resource, but the presentation lacks any context; knowing what episode the images are from would be helpful, for example.

A similar issue hampers the presentation of deleted scenes. Deleted scenes can be great fun: They provide a glimpse into other directions that the writers had in mind for the characters and the story. However, unlike those on competing DVD sets, these dozen or so deleted scenes are presented as a single 24-minute movie entity, without any individual index to jump directly to a specific scene from a specific episode. The scenes are separated by episode, and the writers and producers do provide excellent context on why a scene may have ended up on the cutting-room floor. But finding scenes is far more difficult than it needed to be.

Particularly insightful bits: An introductory expository scene between Carter and Sheppard and McKay detailing why she was chosen to lead the Atlantis expedition, and a two-minute bonding scene excised from "Trio" between Dr. Keller and Carter that delves into their respective personal lives (Carter actually responds in a way that sheds some light on what may have happened between Carter and a certain maverick general in Washington, D.C.)

Each of the discs has at least one 10- to 14-minute special featurette; all but two of these are tagged as "Mission Directives" to delve deeper into the making of a specific episode. Disc one has two: one for "Doppelganger" (a 14-minute bit with Robert C. Cooper) and "A New Leader: Amanda Tapping Joins Atlantis," a 15-minute look at how Tapping's Col. Carter left Stargate Command to head up Atlantis (Mallozzi, Gero, Paul Mullie and Tapping are among those who weigh in).

Disc two has a featurette dubbed "The Doctor Is In: The Return of Paul McGillion" (inside the actor's return to Atlantis after his character, Dr. Carson, was revived), as well as an amusing (though drop-dead hilarious) seven-minute Stargate Atlantis blooper reel—a first for a Stargate Atlantis set.

Disc three has a "Mission Directive" that delves into how director William Waring helped create the subtle distinctions required to depict the Replicators. Disc four includes two Mission Directives, one each on "Quarantine" and "Outcast," and it has "The Making of 'Trio'"—which Wood notes was season four's most difficult episode to film. And disc five contains a short look back on season four's new directions.