Comedy series finales are notoriously difficult to get right. Often they become too serious for a comedy, too soppy or just plain confusing. There are even times when you feel cheated.(Roseanne, anyone?)
A good finale celebrates the essence of the show. This one does that by including as many cameos as possible, offering the viewer the chance to reminisce. (Although, there are always a few missing. Where was Sue Ellen Mishkin?) The danger exists that some characters do not get enough attention. (Puddy was underused.)
The big problem is what to do with the main characters. Larry David chose to punish them for their essentially asocial behaviour. Original, but I felt that there was something wrong. Finally I realized that the four New Yorkers reacted to the crime in the way only George would normally. Jerry, Elaine and Kramer were unrealistically brought down to George's level. That may be why some people felt uncomfortable with this finale.