Perfect Dark Zero is good.... But Perfect Dark N64 I think still holds the title.
The Skedar are possibly mentioned in a scene later on in the game but no one except Jonathan and Mr Carrington from Perfect Dark N64 makes an appearance.
The gameplay is ok and graphics are fine, Music is great but for some strange reason it feels a little rushed for the 360's launch?
Either way, Its only my opinion so dont let it discourage you if you want to get it.
Perfect Dark Zero is a good game that will stay with you on your shelves until the next best thing comes.