I recently tried DirectAdmin and I've fallen in love with it. The interface is great, it's fast and in no way resource intensive (be it CPU or Memory - unlike it's competitors). It's great from a System Admin side since it's not as intrusive as cPanel, you can compile anything yourself, whatever version. I just purchased a $50 VPS from PowerVPS with DA to test further.
I'm seriously considering reimaging some of my current servers, since I'm sure the performance boost will be beneficial and I like having more control, which other CP's don't give you.
Keep in mind this CP wouldn't be good for admins with no Linux experience.
Just my experience, and I'll update you as I discover more.
-Scott
altough i'm just a user from a hosting with DA, but from my experience, i agree with what scott said about DA, they're a bit faster than others, i use others than DA with some of my client. also the navigation from DA is more structured and direct. I just don't know why most of hosting company didn't use them. And one more, DA's dns manager is awesome.
cPanel has more features, but DA is more flexible. If I was in the web hosting business, I'd for sure have to keep cPanel since that's what most users want, but I'm not and I don't.
So, is Direct Admin closely tied to system ? For example, once I tried installing MySQL 4.x on my plesk powered box, and Plesk went nuts after that. I am really against close integration of control panel with underlying operating system/techstack. What would be your opinion about Direct Admin from this point of view ? I'll be installing stuff like RubyonRails, MySQL 4.1, PHP 5.x etc. on my next box. I don't want control panel to be the obstacle in doing so.
Pratik, from my testing with DirectAdmin, the only problem with DirectAdmin and MySQL 4.1 is the "client does not support authentication" issue, which can be fixed by using OLD_PASSWORD instead of PASSWORD. You might need to put "old-passwords" or something similar in my.cnf, too.
I know cPanel supports PHP5 and MySQL 4.1. I haven't tried Ruby on Rails.
I have switched to only offering DA on VPSes as it is just so much faster the cpanel for this, and have also started to offer it on dedicated servers. I am not sure why you say it is not good for unix newbies, this is mostly what I have sold it to. The thing I find lacking is no postgresql support.
For those that know the OS, and really want something with almost no integrations, webmin is also worth a look, since it is free. It is not good for hosting, but not a bad choice if you just want your own server.
DirectAdmin 
