The ending was suprising, even though I had already read up on spoilers, I didn't know to expect such a moving and heroic end to a great character. Then after killing Ross, the title screen revealed to me that the game is as much of a telling of Jack's redemption as John's.
Jack as a playable character, like many have said before me, is annoying, I can understand why they did it, and it was really cool to be on the other side of a tutorial mission for once. The main thing for me is the voice, the fact that John can say the same dialog for 40 hours and it never gets annoying, but within 10 minutes of Jack saying the exact same things as his father, you resort to parking him on train tracks and running off cliffs
Who else, after the ending, turned Jack into a evil character? I've had a time just going around to different towns, commiting a crime, then just shooting all the law enforcement and people firing back (I still have a clean save from before I did this, however

).