This is my own short review for webmin.

First of all, webmin is not a hosting control panel in the true sense of the word -
you CAN configure webmin + virtualmin to manage multiple virtual domains (website, email, ftp, statistics) and it's also possible for other user levels to login to perform their actions - domain owner, email and ftp users.

having said that, webmin isn't developed with the hosting business in mind. the old-fashion (and imho ugly, almost careless) default theme clearly says it.
though uncomplicated and easy to use, user-friendlyness isn't really a thought either.

In reallity, webmin is a server administrator's software. you can manage everything from boot services, running processes, cron jobs, lots of common software (http, database, email, etc), network (including firewalls), hardware... anything and everything can be supported with aditional modules.


Conclusion:

PROS:
- Great for server administration, even if you need to get a decent theme on it ;)
- YOU control your server settings.
- Good for "friendly" hosting - websites/domains for you, your friends, your company, your boss's friends...
- Open source.

CONS:
- Some skill needed.
- Not very appropriate for a web hosting provider.
- No true support for resellers.

i personally don't like webmin ...