So there are two main factors to be considered regarding GIS software. Cost of provision and cost of training. If you are a large organisation you may decide to acquire a multi user licence as a means of controlling costs. If there is a potential user requirement for a hundred users one solution could be to have a licence which allows up to a given number of users, say twenty, onto the system at any one time. Each of the hundred users can have access to the system as long as there is an available slot for them. In this way many more users can have access to GIS capabilities than would normally be the case with a fixed number of licences. As users become familiar with the facilities more seats can be added to ensure that users can access the GIS when they need to. When there are a large number of potential users then training is essential to ensure that the GIS investment is best utilised. Training can be arranged either on site if there are appropriate facilities or at another location with dedicated training rooms.
Whatever is decided upon for your GIS solution and training needs the main aim should be to ensure that all departments that could benefit from using a GIS system have the opportunity to do so. Then at some future point GIS will be as accepted and as familiar within the general office environment in the same way as word processing and spreadsheets are now.