We have a web-based software product that has a growing user-base of around 200+ people.
We used to have our help sent out with the product as PDFs, and then last year we offer both the PDFs and also an online web-help here.
The workflow is not too great.
As developers finish tasks they update the docco as they go in one word .doc.
Before a release, we use a programme to convert this .doc to a series of HTML files which we then upload to our site via FTP.
There are a number of formatting issues (e.g. graphics in word do not port across ok) and in general, the workflow to update the documentation could be better if we skipped out MS Word and edited directly online.
I had a quick play with MediaWiki and looked ok (and not ruling it out just yet), but our users are familiar with documentation in the style to this.
What are the top runners up for documentation platforms out there? - For me, the clients user experience comes first (especially around searching the help) but I would also like to make the developers experience easier to update this docco as well. - Ideally, we need an open source solution.