Re: Quite the planning process, this
But seriously, it can be a pretty big headache in Enterprise. You've got to arrange its removal from x hundred PCs in your organization, you've got to find the budget and organize purchase orders of a replacement, deal with any process changes for distributing updates centrally to whatever new virus vendor you choose. And the necessary meetings, of course. ;)
Let's see... the last place I worked managed about 8,000 pc's. Desktop Engineering took the version of Windows to be used, removed all BS that the company didn't want (such as games, AOHell, etc.) and then loaded in the stuff they did want like Office, certain proprietary programs. This became the master. A copy was sent to the company selling us new PC's and all PC's were imaged from the master. Anytime an employee left the company, their PC's was re-imaged for the next user. If a user has some serious PC issues, many times, a simple re-install from the master OS solved the issues.