In case you were wondering, "The Mary Tyler Moore Show: The Complete Third Season" is on its way this coming January, so the complete series seems likely to come out on DVD.
Watching the long-delayed second season, I was surprised how little it improved over the somewhat disappointing first season -- in fact, it may have hd even fewer real standout episodes than the first (which at least had the brilliant pilot and the first Nancy Walker episode). Really, if "Mary Tyler Moore" had gone off the air after two seasons, it would look like a weak cousin of "The Dick Van Dyke Show," and not nearly as good a short-term creation as "He and She" (also from creator Allan Burns).
Of course it didn't go off the air after two seasons, and its reputation is largely built on the episodes from seasons 3 to 7 -- in other words, season 3 is where it gets good. As to why it got good, it's a combination of things ranging from the arrival of writer Ed. Weinberger (nobody knows what that period stands for) to the relegation of Mary to a less prominent role on her own show, so that the supporting characters finally got to take over and lead their own stories (this was the season where Ted got his regular girlfriend, Georgette, and where Phyllis thought Rhoda was making time with her brother -- leading to a famous punchline). Moore was in many ways the weakest link on her show, and building more stories around the conflicts and problems of the supporting characters made for more interesting stories than Mary's That-Girl-Goes-To-Minneapolis adventures usually could. Although the third season does offer probably the best Mary-centric episode, "Put on a Happy Face," a catalogue of everything that can possibly go wrong for a person before attending an important event, culminating in Mary's awards acceptance speech: "I usually look so much better than this...."