Improved collaboration through multi-user document editing capabilities. Improved governance through process workflows.
The product could be more intuitive both from an administrative point of view and from an end user point of view.
I have been using this for five years.
We did not have any stability issues.
We did not have any scalability issues. However, we have deployed a very simple system, with no bespoke tooling or plugins. We have, as yet, not had to scale the solution beyond adding more RAM or disc to either the database or application server.
Never had to use technical support from Microsoft for this product.
We did not have a previous solution.
Setup was complex. Setting up the solution requires a solid understanding of the various architecture options available. While Microsoft has made significant improvements in changing the deployment method so that it is much more guided, decisions taken at the time of deployment can have long lasting detrimental impacts if the decision is not well understood.
We evaluated Atlassian Confluence (we use both products in house for different things).
Plan thoroughly and well for your deployment and make sure that you understanding the implications of the decisions you make around multi-server implementations for scalability and resilience.