Kohlchan.net is running on LynxChan 2.2.x for over two weeks now. I'd say we're mostly satisfied with what we have now, but there is still a lot of room for improvement.
In the first week there were some caching problems (after rebuilding all post cells), but Stephen quickly fixed them after we provided him with more information. It's also worth mentioning that quotation marks weren't properly escaped in filenames (only < and >, not "), but luckily it was discovered before putting it into production. The load average is very low even above 1000 PPH and no other security vulnerabilities have been found yet.
Prior to LynxChan, we had been using our own Vichan fork for a year, but we decided to leave it behind because of the inefficient posting mechanism (every thread has to be completely rebuilt and written to disk after each post), the poor upstream maintenance and most importantly because of that fucking footer which is required by the license. :^)
If you're planning to move from Vichan to LynxChan (or you want to start a new imageboard), here's a list of things you may want to know first:
1) Files stay in the DB after (automatic) thread/post deletion. There is a "weekly prune" which locks the engine due to possible race conditions, but it may be slow for some servers. On the first run it took at least two hours to prune ~30GB. That's why we're now doing it with a cronjob three times a week and it now takes only about 10 to 40 minutes each time. Having an SSD and using XFS as a filesystem may also speed up the whole process significantly...
2) LynxChan's moderation capabilities are inferior to Vichan. The only advantage LC provides is the media management page which gives you the ability to moderate the most recent files, and filter them by orphaned (no file references) and name. Stephen wrote an addon for us to implement post history, global search, virtual IP addresses for anonymous users (so that you can invalidate/ban their sessions), proxy detection with DNSBL + AS and individual file deletion/spoiler. Version 2.3 will include those features, too.
3) Range bans last indefinitely (no appeal), and it's only possible to ban /{16, 24} for IPv4 and /{64, 96} for IPv6. Therefore you have to disable IPv6 if you don't want the best computer scientists of your chan to come back after each /64 ban. That will be improved in LynxChan 2.3 as well.
4) In contrary to Vichan which provides a relatively good-looking frontend, LynxChan's Penumbra looks and feels horrible by default. Maybe this should encourage imageboard admins to modify it themselves? I don't know. But you can also just fork KohlNumbra: gitgud.io/Tjark/KohlNumbra (contributions are always welcome)
5) LynxChan's template engine is not very powerful and there is no i18n either. Adding another template engine on top of it may be advantageous.
6) Use gitgud.io/LynxChan/VichanMigration to migrate Vichan's MySQL database.
7) Phoneposting will reduce due to missing support in Dashchan and Overchan. That may be a good or bad thing depending on your personal beliefs. However LynxChan is mobile-ready with its API and I believe somebody will definitely implement a mobile application sooner or later.
8) Addons / modifications are very easy to write, but porting them to the next version may be time-consuming.
That's pretty much all there is to say. It's a fast engine with a lot of features and most things I'm complaining about will be fixed this year anyway (& a subset of that is already in kc-addon). Just try it out for yourself. The installation is even easier than Vichan IMHO because you just have to run one script and it will do everything for you (except installing the system requirements obviously).
