Re: should software be a controlled document?
Software should be controlled but the extent of the control should depend on it's function.
We operate change control similar to a document control system for the software that my company produces as a product but thats very different to the software used to run a business.
Your IT department should ensure that patches, upgrades etc. are carried out in a controlled manner but which version of software you are using doesn't matter a great deal as file formats can often be read by many different applications, MS Office for example is generally comptabile between Office 2000 - Office 2007 and alternative products such as Open Office can also read ms office formats, so here which version of software you are using doesn't matter a great deal unless people are going to be using the very newest features.
I suppose what I am trying to say is that if you use an old version of a document, internal or external, you could be in real trouble where as if you use an old version of a software product it's unlikely to matter, or even be noticed.
The main reason I wouldn't include software application in document control is that THEY ARE NOT DOCUMENTS
I would see sections 6.1 provision of resources, 6.3 Infrastructure and 6.4 Work Environment as the relevant sections for software.