We tried running it, so a lot of experience with it, and it wasn't great. It barely stayed online.
For something so simple, you have to run a massive server, like gigs of ram and multiple core, even with a very modest user load. Take a look at the codebase, it's also a mess and impossible to fix any bugs. Finally, if you want to get your data out or report on the message activity, good luck, you'd be better off passing paper notes around. The open source version is nerfed a bit too, no LDAP authentication for instance, so it creates a lot of problems there too.