Some day ago, I installed RoundCube Webmail on my server to test this new exciting webmail interface.
In the past I used SquirrelMail as my main Webmail interface. I tried Horde/IMP, but I really did not like it, because its installation process is very difficult compared to SquirrelMail and its user interface is not convenient.
Performance is the only issue which should be improved. Regarding almost all other qualities of the software you would not think that this is still a 0.1 beta release. The guys from Microsoft who developped Outlook Web Access should really learn a lesson from this software.
The roadmap of RoundCube is very promising and makes me expect even more cool features.
Although it is still a beta relase, I think RoundCube webmail is ready for restricted production use. Of course I will keep an installation of SquirrelMail on my server as a fallback for clients that are not AJAX capable. However anyt I want to check my e-mails from a computer with a modern browser and broadband internet connection, I will prefer RoundCube.