During these days I have been testing it. For me is OK because I use Debian and Paypal. It seems stable and fast, but the look and feel is extremely simple.
I read that it will be improved in the panel homepage.
I'm one of the lead developers for GNUPanel. Here's a little bit of information that might help you to decide:
* GNUPanel is very Debian centric. I have a port nearly ready for Ubuntu, however it is on hold.
* While it does have a billing system, it is rather basic. You would have to do some hacking in order to have it work properly with software like Modernbill
* It is not (yet) as feature rich as Cpanel.
Currently, GNUPanel is in a cathedral style ground up re-write. We're doing this while translating the database tables and functions from Spanish to English. While we're at it, we're adding a very easy to use plug-in system (i.e. make your own Fantastico easily, hack the biling system independently of the panel, etc). We're also adding hooks for multi-server (clustering) support and Xen virtualization.
Our goal is as you said .. we want to make a "C-Panel" that hosts can modify and share without the hassle of restrictive end user license agreements.
GNUTransfer, the company behind GNUPanel is using it in production on their shared and VPS offerings, they have a lot of happy clients. In its current form it is very stable, but clients used to C-Panel might not like it.
By the end of the year, a new beta candidate will be out with most of (or hopefully all of) the features I described.
I use gnupanel on a production server at <snipped>, I've now created an automated order script and will be working over the next couple of days... Also I have updated some of the addons such as wordpress to the latest version 2.61.
It's easy to install sure? I'm asking on the forum also about the option to have auto-creation for the orders, it's a good extra, but they are not offering under gnu.
Ive now created a addon to the panel that allows a customer to be able to signup for an account at my site webvolorem.com/signup then they are taken to paypal to make a subscription payment, once payment is complete an email is sent to the customer with name servers etc they have to set (done by paypal ipn ). If payment does not complete checkout they will not be able to access there account.
I have also created a simple password reset script so that if a user forgets there password they can have it reset with a random one and emailed to them.