What really pisses me off about it after rewatching the first 4 seasons after, is that Jack had a lot of opportunities to return to the past that he ignored to save people just in case it didn't work.
Then in the finale he doesn't even stop to think what would happen if Ashi sent them to the wrong time period or something, he just goes with it. Its a slap in the face to all the other times Jack could have just returned to the past.
Not to mention the fact that I can't see one person who either A) Didn't like the Scottsman or B) Not like Jack and the Scottsman's interactions, and yet all we get is barely a minute of talking between the best duo ever.
It has a lot of problems, and it was rushed. Genndy should have ended it a lot differently over a few more episodes.