I'm trying not to give anything away (that hasn't already been all over the media), but still...
OK, I confess - at first I found it maddening (my first email to a friend and fellow addict read simply: ARGGGHH!!!). But in retrospect, I think it was perfect. The sense of dread kept me on the edge of my seat throughout the show -- and gave me nightmares that night. In brief, I read it as Tony gaining an increased sense of his vulnerability. And considering that he has no innate sense of security to start with (unloved by his mother, who ultimately tried to kill him, how could he?), that' s saying quite a lot. Add in that he has now witnessed the impermanence of everything (Junior's dementia), and that his primary goal has been to protect his family, but that he now realizes that he has made them more vulnerable (AJ's suicide attempt, Bobby Baccala's murder), and the pain becomes excruciating. The little ironic note, that AJ has to remind him of his own good advice ("remember the good times") may sound banal, but it's also the only way to survive.
That said, I found the Phil Leotardo speed bump death extremely satisfying.
Oh yeah - and there was a cat! Maybe that's really why I liked it. Remember, Kit can be a nickname for Christopher....