Most KITH fans agree that there seemed to be a swoon in Season 4 driven by a lack of creative spark. I would have to concur. While the troupe have rounded out their performances by this season, the material itself drops off. Still there are high points and I think the idea was that they were hoping to be more daring as shown but their lack of reliance on the old standby characters. Many of the recurring sketches are new, such as the socially edgy "Steps" featuring a group of gay men hanging out on the steps shooting the breeze.
The format is well-established by now: 4 discs; 3 of epsiodes; 1 of "Best Of", commentary, rare performances and everything else to which we've grown accustomed.
Personally I think it's worth owning. If you have the other 3 sets then why not just keep completing the collection?