Such an exciting and shocking season ending!
This season gave me some great moments, including the return of Irina, Vaughn proposing to Syd, Jack's always-interesting character progressions, Sydney playing her mother in a recreation of Jack's marriage, and confirmation of my belief that Sloane had truly reformed. (That was an underutilized plot device: The emotional tension of a reformed Sloane doubted by everyone else could have been delicious. Particularly if Syd and Jack realized that he was reformed just as Sloane, beaten down by their doubts, returned to his evil ways.)
The downside this year was a weaker season on the whole. The beginning concerned me, where last year's season finale was essentially discarded and a new story crudely pressed into service. The first half of the season was lackluster, but the excitement returned. But, this was tempered by a cheap plot device of reinterpreting past stories in light of a new villain, in order to quickly move the Elena story forward. But it felt forced, and left me with an emotionally unsatisfying bad guy and an end-of-the-world scenario less interesting than the fall of SD6 in S1.
Finally, the finale. It was exciting, but generally Alias' plot twists are rooted in existing story. This one, Vaughn not being Vaughn, felt totally random and threatens to (poorly) apply a reinterpretation of past episodes in order to make new stories work.
So, next year: Since its likely the last season, I hope J.J. Abrams gives Alias due attention and crafts a masterpiece of intrigue, spycraft, excitement, and stunning resolution!