For an intranet, you will probably have people from many different departments with varying degrees of technical skills contributing content. A product that relies on scripting to manage workflow, templates and content tends to be more flexible, but one that has a graphical interface will be more accessible and easier to use.
Some products require their own servers or run only on specific operating systems.
And you may have to set up an Oracle or other database server to store your files. In any case, you may be forced to purchase and maintain more equipment or software. With a large or highly customized implementation, you may not be able to avoid adding to or replacing your existing IT infrastructure. In some cases, it may even be desirable to throw out an old system in favor of the new content management system. Whatever your situation, be sure to take into account the implementation and maintenance costs associated with new hardware and software.