Let me give you my take on this whole thing.
The "plot holes" that everyone is talking about were left that way intentionally by the writers to give you something to talk about. Something to ponder until next season. They always leave little things unsolved at the finale. Remember everyone wondering whether or not Christopher Henderson was really killed?
I understand that you may not consider the circuit board a little thing, but in reality, it is. That was a storyline fetched out of no where because the writers had no idea what was going on with the season. The show took a serious turn around hour 17ish. It tried going back to its roots with making the show about Jack again and his personal vendetta.
I don't think next season will have anything at all to do with this season, except for the last 5 minutes. Those were so crucial to the development of Jacks character, especially considering where he was at the begining of the season. As Sutherland himself said, at the start of the season Jack Bauer was "indifferent" to everything. This has shown that he has come back to reality. He can not live the life he wants with his career. However, he can not live his life without his career. Ala Heller saying "You tried walking away from it before".
I loved Jack yelling at Heller and showing how fed up he was by the Governments treatment of its people. He himself was becoming a product of such behavior, like when he has to make decisions for the better of the country (killing Curtis).
That whole last scene was Emmy worthy for Sutherland. He showed how screwed up and lost Jack Bauer really is. And how about the line "If you send someone after us, I'll kill them. I'm pretty good at doing that too."
Jack walking over to the cliff with his gun was the cliffhanger for this season. Literally, considering he looked over the cliff. But, creatively, the cliffhanger here is what will Jack do next. Will he take his life, will he stop doing this job, will he disappear, etc, etc.
I really liked it. I think it was the best possible finale for a season that was generally weak. In fairness though, my only problem with this season was that up until hour 17 or so, as I said before, the show was going no where. Jack Bauer felt like a guest star on his own show. But people are forgetting we saw buses blow up, Jack kick a guy threw a subway door, a nuclear bomb went off killing 12,000 people, more attacks, Curtis' death, Palmers assassination attempt, and so on.
People wanted something big to go down in the end, but really, the writers have now ridden themselves of this season. They no longer need to go back to it considering all the MAJOR events have been tied up. No more Chinese thank god. They are starting fresh next year, like a new series.
Oh, by the way, more evidence of the writers trying to screw with everyone: the zoom in of the chinese secret service guard when Karen Hayes left her holding room.
