My short answer is:
- To demonstrate so called 'ROI', it is always useful to show overall usage (e.g. no of hits, no of contributions). Coming from a library and information science background, information and lbrary professionals know that usage/hits does not mean 'users getting the help they need', however, many senior executive/board members do like to read the numbers, so give it to them.
- I find the tracking of search query useful, as I look at the search queries every month and ask myself 'if users are looking for something using these search queries, does our intranet give them what they want?'
- To drive continuous improve, I think intranet team need to really understand what users find useful (or not) as part of their day-to-day work. Look through the users' eyes (not the intranet designer's eyes). Ask users to talk about their work and how they got help (and see if the intranet is even mentioned!). Don't ask them a direct question such as 'how does the intranet help?' The intranet should come out naturally if it does help them to solve problems, get ideas, access information.
So here is my suggestion, give the quantitative figures to decision makers, and listen carefully to your users' voices if you want to drive continuous improvement beyond looking at usage figures.