Nazi Zombies was a big hit with CoD: WaW but was later replaced by spec ops, which there's nothing wrong with. In all honesty I would rather play Zombie mode.
The multiplayer options for Black Ops has been very "under the radar" for a while and they're just waiting to reveal a new multiplayer feature to us. Nothing specific has been said about it but during an interview Josh Olin, community manager for black ops, stated that if there was going to be a Zombie mode there would probably be a trailer soon. At the same time Brady Games has a paid strategy guide which they said to include a Nazi Zombie mode, which could very much be a mistake.
What would you rather, a Spec Ops mode or Nazi Zombies?