I think that Open Source GIS is a wonderful idea. The concept and tools are excellent. My only gripe is that you need your GIS Analyst or Specialist to be a developer to deal with 'bugs' the complexity of using this software medium.
The thing is that you are asking a GIS Specialist/Analyst to be an Analyst as well as a developer in an organisation.
Personally i rather work with a solution that i have support for and will get it fixed asap. The costs as well to me are dependant on the Organisation. Evidence will sugegst that more than 3/4 of the major companies will prefer to use a software system that is reliable and will be secure, userfriendly as well as being able to deliver appropriately.I think that opensource has fiunctions that are overly theory based and some of the functions are nor relevant to a solution and business day operations.