While the main downside to most of the proprietary appliances is cost, the benefit of a proprietary system like a Panasonic or Kalatel system is that it's extremely reliable, and it's hard for someone to break.
The current trend in the industry is to go to distributed solutions, putting more intelligence, and even the recording capability in the camera.
For example the distributed video surveillance approach used by Iron Sky for metro-area surveillance shows us how to use video data as a crime-fighting tool, and their approach has benefits for the enterprise as well. (No I don't work for them!)
My experience has been both on the proprietary stuff like Panasonic, Bosch, GE/Kalatel, and on the Windows stuff, mostly Netrome, GeoVision, and ZoneMinder.
The big thing to be careful about is that the system that your design has the level of reliability you require.
All too often, the Windows-based solution will be hosted on a single-power supply no-name PC without even a RAID array or a UPS backing it up.
Of course that system would be cheaper than a GE-Kalatel DVR, but after a year, the PC power supply fan will seize and the system goes down.
I've found that if you build a server-class PC, add either a Linux-based system like ZoneMinder, or a Windows-based system like GeoVision, you get a stable full-featured solution.
Personally I never considered using a Mac for this, but I guess you learn something new everyday.
I would be interested to see how the open-source Linux PC application ZoneMinder stacks up against the Mac solution??
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