I regard "The Sopranos" as one of the masterpieces of American television, and on the whole this final (semi-)series is well up to standard. The acting is uniformly superb, and the constant promise of violence, as ever, makes for compelling viewing. Nevertheless, I felt there was something rather "bitty" about the plotting; in previous series the narrative has revolved around a single character's story (Pussy, Ralph, Adriana, Vito); here, there is no dominant character, so the narrative impetus isn't quite so great. Also, one or two episodes have a slightly "soapy" quality, with plot dictating character rather than vice versa (the denouement of Tony's relationship with Dr. Melfi is very contrived; and where did Tony's gambling addiction come from all of a sudden?).
The writing is, as usual, excellent, though I felt it wasn't quite as subtle as in some of the earlier series.
As for the bizarre ending: I hope the obvious interpretation is the correct one, and it's not a case of the producers themselves not knowing what happened. Certainly a mood is set that invites a particular interpretation, but I shall say no more.