Yes, the Sopranos is an accurate depiction of life in the Mafia, because the Sopranos seems to coincide with what we know from the Mafia. Of course, no television depiction is completely accurate, and the Sopranos isn't either. But the intimidation of people that go along with the Mafia as well as extortion, is accurately portrayed by the Sopranos.
The Sopranos were as close as you would get into the mafia life without being involved in the mafia. They are crooked as can be and into all sorts of illegal activities and always trying to find a way to get away with something. They will whack whoever it is no matter what.
The Sopranos is closer to an accurate depiction of Mafia life than many other series or films due to the lack of restrictions on HBO and the advantage of the long-form format of television, but it is ultimately less about Mafia life than about masculinity, and David Chase borrows more from Bergman and Fellini than he does reality.
Be it a show about scientists trying to fall in love or a detective following the preternatural, all television is written, produced, directed, and acted out. In other words, nothing in television shows is real. The Sopranos, like shows that depict medical emergencies or legal proceedings, tries to show in a ‘realistic’ passage of time the heartaches of the personal issues faced by Mafia families and individuals in a believable way. In literature, this is known as emotional appeal and sensory appeal which is used frequently even in newspapers that report on ‘current events’ that are really occurring. The truth is, no written work of fiction, be it historical or contemporary, can accurately depict anything particularly when it is brought to the world of television where even the look of human flesh is no longer realistic and is altered by lighting, make-up, and stylists as well as costumes. While The Sopranos may come very close to depicting the lifestyles and trials of those bound to a life of organized crime, it cannot be an accurate depiction so long as it continues to use any synthetic means of conveying the ideas and events. One of the greatest things about television and film is the ability to transport a person into a world that they could not themselves reach in their everyday life, but when those worlds are meant to be some that actually exist around us, the lines between reality and produced stories become blurred for some and painfully obvious for others, but they exist. The bottom line; never believe anything you see on a television show that has had a ‘writer’ in the credits because writers place their own perspective into the mix and then it becomes an entirely different depiction and not an accurate portrayal or natural look at all.
There are probably some elements of the show that reflect mafia life, but for the most part its a fictional show that is intended to entertain more than educate. Sure, mafia members have families, and need to balance their "work" and home lives. But I don't think the actual business of the mafia is accurately depicted in the Sopranos.