Firstly, Larry in IT saved my arse this week, persisting through a long, poor quality phone call to fix a remote login issue,. All hail Larry.
Secondly, I've been in tech comms a long time, rising to consulting writer and info architect. I use Excel all the time for documentation. We write using XML and methodologies such as topic-based authoring for content reuse and re-purposing. I have not found a better tool for doing the initial architecture design and for creating topic lists and outlines. Best of all, under the covers the content is all tagged in XML so I can export and filter it for import to other XML authoring tools.
I also export content from other sources (even code dumps) to sort and organize in Excel - such as all the error message strings.
And, yes, Ive done entire documents in excel because it can handle dynamic content that works on virtually any windows box - I don't have to worry whether the user has that tool.