Among the most useful features I like are: the site permissions (distributed governance model), the social enterprise features (micro blogs, activity feeds, community sites, Following, Likes and Reputations), app store, search and query, external data access, security, site management and site customizations.
Improvements to My Organization:
It's been a process-improvement catalyst in the sense that it enabled and empowered real-time collaboration and dashboard tracking of business intelligence reports and performance analytics. It's certainly reduced the number of hours needed to create, update and maintain worksheets and forms hosted on legacy systems, databases and it also reduced overhead on obsolete file repositories.
Room for Improvement:
Well, for SharePoint Online, the add-on features which are free tend to expire within a month or earlier. It would be great if these free add-on features would last longer or last permanently.
Use of Solution:
I have been using SharePoint since 2012.
We have not encountered any deployment issues, fortunately.
We have not encountered any stability issues.
We have not encountered any scalability issues.
The customer service I would rate a 3.5 out of 5 (5 being highest); responsive, timely, proactive.
The tech support I would rate a 3.5 out of 5 (5 being highest); responsive, strategic, proactive and precise.
We used an open-source CMS (Joomla-based) and due to the limitations, we switched to SharePoint.
Very straightforward setup and not that complex.
We used our in-house support team to deliver the implementation.
Cost and Licensing Advice:
Do your due diligence first and conduct an in-depth discovery session with stakeholders prior to designing your solution that uses SharePoint as a platform
Other Solutions Considered:
We evaluated Alfresco and Confluence, and then decided on SharePoint.
Ease of use, ease of setup, ease of administration, ease of configuration, ease of customization... what's not to like? SharePoint's got exactly what you need. Just don't expect too many frills, bells, whistles in terms of UI, but even then, it gets the job done.
Disclosure: I am a real user, and this review is based on my own experience and opinions.