The AV Club has started covering classic Sopranos episodes, which has finally given me the motivation to start watching. Some thoughts on the first season:
The Sopranos is built around tension, but it's a formal tension more than a narrative tension. There is a narrative tension, certainly, involving Tony Soprano attempting to navigate his life as a mob leader with his family life, amongst other things. The formal tension comes from the show's framing device and initial pitch: "a mob boss goes to see a psychologist...." The show walks a fine line between the psychological aspect of the story, which is metaphorical, and the actuality of Tony's life, which is literal.
Most art is, in some ways, metaphorical. It's designed to allow the viewer to fill in the blanks. On television, for example, Buffy and her friends don't start out in high school, they start the series in "high school." Though nominally sophomores, they're played by actors and actresses in their late teens or even early 20's. Then again, the show is based on metaphor, using supernatural horrors to stand in for the horrors of high school and later, young adult life. The dialogue goes along with this. Xander, who is supposed to be the geekiest of geeks, is consistently clever and witty, but he does so in a way that represents social awkwardness.
On the other hand, a show like Freaks and Geeks takes a more literal approach. The "geeks" of the title are supposed to be only a year younger than Buffy's group, but the actors are obviously closer to their nominal age. Their social awkwardness actually manifests as awkwardness on-screen. There's still a great deal of metaphor - it's network television, after all - but the stammering and fear actually manifest as a somewhat authentic high school experience, instead of "high school." I'm not saying that a literal approach to television is necessarily better than a metaphorical one - that would be foolish for science fiction fan! - just that it's there.
The Sopranos uses both, though. Tony's interactions with his shrink, Dr. Melfi, are almost entirely metaphorical. They're "therapy" more than therapy. Everything has a direct one-to-one correlation: Tony hallucinates an ideal mother figure when his conflicts with his real mother reach their peak, for example. Tony's interactions with Melfi are generally entertaining, and the idea of 90's therapy, when random drug prescriptions were at their peak is certainly good story fodder (why is Tony on lithium? Why not!). However, the rest of the series is at its best when it's understated and literal. Tony's interactions with his family, for example, or him hanging out with his crew talking about The Godfather.
As the season progressed, I found myself more and more frustrated by this tension. The best episode of the season, "College," was totally therapy-free, and was riveting television. A couple eps later saw "Boca," which took the metaphor outside of the shrink's office, and suddenly had a soccer team, soccer coach, new friends, and a sexual abuse plotline that were all vaguely surreal - and it was easily the worst episode of the season.
The therapy sequences made sense in the pilot. The entire show was a simple pitch: "mob leader sees shrink." For a pilot, this makes sense, as it's like a movie that's asking for sequels. But over time, it becomes a device or worse, a gimmick.
Yet by the end of the series, I found myself less frustrated with the therapy conceit. The Sopranos is a show about its metaphors as well as the literal. It's going to have goofy dream sequences, ham-handed metaphors, and blatant TV-style artificiality. These things don't lessen the show, they force the viewer to watch it critically instead of simply for artificiality, and that way the viewer can see the intentional cynicism and darkness that the characters and setting exude. To put it simply, without the layers of metaphor and formal tension, it would be easy to simply declare Tony Soprano a hero or a villain, someone to root for or against. He is the reason to watch, and the artificiality makes me, as the viewer, say "Why am I watching this? What makes it good and interesting?" And usually, the show has answers to those questions.