I am wondering if there exists some kind of whitepaper or best practice description for managing let's say 30 firewalls spread all around the globe. We have a regional office in each of the three regions EMEA, Americas and APAC. Currently we have three stand-alone installations of NSM with each region managing "there" devices. This is kind of "not good" because it is more likely that objects and rules etc. will be different over time .
Another possibility for this would be to use one NSM installation and configure domains for management of each of the regions devices. Super users can specify the rights of the domain users and can create objects policies and the like in the subdomains for the regional admins to use.
Probably slightly easier than CM and might save you the cost.