Yes and no. The answer will depend on which features you need. Here's a short comparison of the features that Citadel does and does not offer:
- The ability to view and compose messages via the web interface
- Formatting of messages with rich text via web interface
- The ability to access messages via imap, and to search them via these facilities…
- Posting via email to a forum
- Narrow user access control
- A themed web interface
- The ability to use it without having apache or php / perl installed on your production system
- Interactive intra-forum chat capability, in addition to standard posting access
- A room overview with aging news topics. However, Citadel rooms have topics that could be used to do that.
- Unauthorized message reading
- A threaded message view
- Moderation with a scoring system
- The ability to view your avatar in board postings. However, a picture can be uploaded to your profile for viewing
So in conclusion, Citadel scales quite well if you have a rather fixed group of people that want to sign up with your server, have comments posted on their work-outlook (and maybe have limited access to internet connectivity), and discuss topics in a cooperative manner. However, Citadel does not scale that well on a loosely coupled community that just wants to read some news and maybe post some comments in the future.