I was reading the enities.def file that is included with 2.3
It's really good reading for a noob mapper like me, but I am confused by this:

Portal camera. This camera is used to project its view onto a portal surface in the level through the intermediary of a misc_portal_surface entity. Use the "angles" key or target a target_position or info_notnull entity to set the camera's pointing direction.

I thought nexuiz does not support portal cameras if so why is this in the ents def?
Or is it some sort of q3 legacy thing.

Is the entitites def file a good indicator of what does and does not work in Nexuiz?

No, it's just that tZork and Tymo weren't very thorough when they modified the Q3 entities.def for use in Nexuiz.

Yes portal cameras are impressive, I hope that they, along with other more interactive features [triggerable trains!] will be implemented in Nexuiz.