I registered here just to post this
Few years ago I was looking for a wiki solution for work. I tried Confluence, Socialtext, Dokuwiki, Twiki, Mediawiki and Deki. My findings through all that discovery was this:
Best user inferface and ease of use goes to Confluence, Socialtext and Deki.
The stupid obnoxious sales people from Socialtext and Deki quickly made me put them on the no go list. Confluence on the other hand was way better, I was not contacted by a sales person but by a friendly technician who just asked how my trial was going, if I had run into any problems she could help with and where to get support.
Twiki was amazing feature wise and the huge community behind it but it lacked polish and friendlyness. Also it was a pain to set up, documentation was of typical open sourceness, lots of detailed info but also lots of gaps.
I liked Mediawiki mainly for two reasons, very familiar interface for Wikipedia users and since Wikipedia runs mediawiki the support for Mediawiki would never ever die for as long as Wikipedia will be running (highly doubt they will migrate away). It lacked two things, propper LDAP support and access controls.
Dokuwiki was nice but nothing special, loved the fact that its file based.
When it came to presenting it to the rest of the company I had two options, choose Confluence or Mediawiki, I did not choose Twiki simply because it would have required too much time learning and customizing to please everyone. So I choose Confluence for its ease of use, feature sets and support and I choose Mediawiki for its familiarity to most (people hardly knew what a wiki was unless I added "its just like Wikipedia") and it was open source and free.
Convincing people that we needed a documentation system that was not built on word documents, text files, excel sheets and basicly whatever each person liked personaly was a pain in the ass. To get anyone else pumped up was impossible so I just stopped trying.
Instead I opted of installing Mediawiki (free) and just started using it myself. Slowly I managed to convince the few people in my department (network/system administration) to use it. I was still the biggest contributor but it became normal that the wiki was the first place to look when we had to search for documentation. After I added a what you see what you get editor it become even better to use.
Now, today, this year, I have switched to Confluence since they offer a 10 user package for $10, perfect to replace the Mediawiki setup. They even have a "universal" wiki converter to convert the old Mediawiki installation into Confluence, and I say "universal" since its just one way, from all major wikis into Confluence. I also added Gliffy for $10 for 10 users, no need for Visio anymore
:)
The support for Confluence has been amazing, just go to
http://support.atlassian.com/ and make a ticket and within 24 hours for even lowest priority tickets someone is there to help you. Best support by far I have received.
Confluence documentation is excellent and very detailed and about open source, Confluence is in a way open source, when you buy it you get the sourcecode as well which you are free to modify as you wish but you are not free to release it.
We also bought a 10 pack of Jira and the integration between Confluence and Jira is very nice.
The next step is convincing the rest of they company that they need this. Should be easy now after I have prooved that a wiki is a very powerful tool for documenting
:)
To end this I just want to point out that when selecting a software solution you must take into account every aspect of having it around. How much it costs to start with, how much time you have to spend getting it to run, how it is to use it from the user perspective, how it is to use it form an administration perspective and if all fails, where do you get help. Open source is good in general, but for companies running open source software can be more costly than other solutions in the long run.