I have been involved in the back end development of SABRE (http://www.sabre-roads.org.uk) for about 7 years, that was originally set up in 1999. The site talks about the British and Irish road network (preferred driving routes, traffic signals, engineering standards) and is predominantly used for the discussion forums.
Over the past few years, a number of longstanding posters have complained and / or left, believing the site is no longer fun or enjoyable. We discovered that there are numerous posts that do not violate any reasonable off-topic and civility posting guidelines, but are still excessively negative or trolling and lead to an unpleasant atmosphere. (Example : http://www.sabre-roads.org.uk/forum/viewtopic.php?p=826961#p826961) I’ve been aware of Discourse for some time, having been a regular reader of the Coding Horror blog for years, so I’m interested to see what it has to offer.
The site currently runs on a Linode cluster running phpBB3.1 and MediaWiki 1.20 under Debian Linux. There’s quite a bit of custom code (mostly PHP with a side order of Python) to provide a seamless login between the forums, wiki and other pages including the maps area which I wrote. Since Discourse is written in Rails, that immediately means I would need some good political negotiation to explain why I want to put more software on the server, and who would support it if I get run over by a bus (there are enough people around who can support a LAMP stack, but that’s it). Another key requirement is that all data must be kept (over 800,000 forum posts and 130,000 wiki pages by about 2,000 users) and upgraded to any new system in a short amount of time (typically no more than an hour or two). I am sure that migrating this data is not impossible, merely time consuming?
Does Discourse suit our needs? I think the hardest problem is not a technical one of migrating data, but convincing the users that we need this solution.