Darrell Etherington has an interesting cyn.in review on his blog at WebWorkerDaily. He points out that people looking out for a pure collaboration platform will find cyn.in tailored to their specific needs compared to Liferay. Which is true, as Liferay offers a full-fledged end-to-end portal, CMS and collaboration solution while cyn.in concentrates on out-of-the-box enterprise wide collaboration.
Overall, Cyn.in seems like a fairly powerful tool, especially if your users are knowledgeable and experienced in customized enterprise collaboration software... I’d recommend Cyn.in for consultants working with larger, established companies looking for an alternative to their current collaboration solution.
He has blogged about his experience of using cyn.in. You can read the entire post here: http://webworkerdaily.com/2008/12/31/cynin-more-open-source-group-collaboration
Thanks for the extensive review of cyn.in, Darrell!