I was not that familiar with Kunena but I felt the need to switch forum products so I downloaded and starting using Kunena. I had always heard that support at Kunena was not that great, but my experience has been otherwise. Support has been available in very reasonable time frames and they seem genuinely interested in helping users of Kunena when they run into issues.
Switching to Kunena turned out to be a good move. Even though Kunena was not my first choice, end the end, it turned out to be the best choice. The developers seem sincerely interested in upgrading their product to meet the needs of the Joomla! community. They also are committed to keeping their product freely available to the community at no cost and I'm not sure that this can be said of other forum developers.
I found JE Story and adapted it to use as a user submitted knowledge base extension. Had a minor glitch (self inflicted as it turns out) and support found my issue and got me going. This extesion is simple, does what it says and comes with great support.
The thing I like about this extension is that although it was designed as a story submitter, it can be easily used for other things. Free is great but the free stuff I tried didn't work. This one is a tad pricey but it works, works well and came with first rate support. Combine those together and it is easily worth the money.