I think the beauty of this episode is that, from our perspective, each character has changed dramatically, and I was delighted to see their new personalaties, both shocking and interesting; in some cases, even, they are more appealing than their originals.
Also, several things we anticipated were made clear; for example, the imminent explosion has occured; the Heroes have failed their mission, and the world has descended into chaos; the entire prospect is very appealing, and put across very well. It is now obvious that, in the present time, Linderman is wrong. The explosion will not unite and heal the world, but send it into an oblivion perhaps irreversible.
Future Hiro's history is revealed, and we discover it is more than the explosion that has changed him so substantially; the loss of Ando, in the explosion, sent him into an obsessive mission of reversing the effects of the bomb, and to visit Peter Petrelli in the episode Collision. Seeing this Hiro, a forceful, dangerous person, was fantastic, and a true testimony to Masi Oka, who pulled of both this Hiro and the original in fantastic fashion.
A true example of circumstances having changed someone almost irrevocably is Matt Parkman, who has become a ruthless, misguided personality, having found the respect he so long sought and working as Head of Homeland Security, under the rule of the disguised Sylar, who, as Nathan Petrelli, is masquerading as the President.
When that was revealed, the show had reached a new pinnacle of revelation and fantastic plot twists; I was staggered.
The acting of all the cast was superb at the least, and is more than commendable.
Some say nothing was learned in this episode, and I feel I should alert them to how wrong they are; for in this episode, you become truly aware of the consequences the Heroes' failure may bring about; the disintegration and destruction of the world, and themselves.