Score 8.9 out of 10. Invader Zim was a great, if inconsistent series. There are some truly hillarious episodes on this set, which make it worth owning, and many that are just O.K. There was only one episode that bored me, and I'm sure it has it's fans.
Here are the best episodes, in kind of an order of how good they are: (note, these are rated by being funny, which is when Zim is best, action oriented episodes are also present, but not as good)
The Nightmare Begins
Zim Eats Waffles
Walk for Your Lives
Parent Teacher Night
Tak, the Hideous New Girl
In addition, here are some kinda funny episodes that are not as hillarious.
Dib's Wonderful Life of Doom
A Room With a Moose
Door to Door
The Sad, Sad Tale of Chickenfoot
The rest are just O.K, but the really good episodes, when watched back to back, can have you dying with laughter, which are enough to make this set more than worthwhile.
For extras, you get a crapload of commentaries featuring various people from the show talking over each other about the show in general and, occasionally, the episode you are watching. For some reason, these commentary tracks are accesed from the audio menu. There are animatics, which you can watch if you are an animation geek or have a crapload of time on your hands. It also comes with the most pointless special feature ever: Irken subtitles. Spelled in the native language of Zim's race, they are little more than a stream of gibberish at the bottom of the screen. The only real special features are a series of three interviews with the voice cast, writers, and production staff respectively. The interviews are good, but creator/writer/head writer/executive producer Jhonen Vasquez, and Producer/Director Steve Ressel are noticably missing.
Show Score: 9.2 out of 10
Extras Score: 7 out of 10
Overall:8.9 out of 10