Agree. I liked the ending. There were very few options available to end the series in my opinion. Since the movie option is on the table they couldn't kill Jack (my preferred ending). So leaving him injured and running from EVERYONE is the only way to do it (very similar to the way they ended season 4 where Jack ended up in Mexico at the start of season 5). The intensity of the show was really back for the last 4-5 hours. It was everything that made the show great.
This is one that I will really miss from my regular viewing. But as you say, all good things must come to an end.