The ending was absolutely perfect. Not only was it the best and most effective implementation of a flashback segment into an episode of any show I've ever seen- in a way that fit the story, no less- but the entire episode, and the very ending, embodied everything the show was about. These were imperfect, selfish people who pretty much ended up getting screwed over by the end of each episode. Instead of going for the lovey-dovey pseudo-tear-jerker like most sitcoms do for their series finale episode, the Seinfeld crew get the ultimate screwover: thrown in the slammer. People used to the typical finale episode expecting Jerry and Elaine to get married, George to find the perfect job and become a millionaire, and Kramer to permanently pursue an acting career in California were going to be disappointed; but Seinfeld's finale was absolutely fitting for the show, didn't compromise what the show has always been about, and I felt was pretty well written.

I would have preferred a different kind of trial. That is, that the characters died in a plane crash or something and went to Hell. THAT would have been "the ultimate screwover".

Hell would be interesting, but I am sure they didn't want to kill off the characters in the event NBC threw enough money at them later on to make a reunion special worth their time.