We use RVSKIN on all our servers. Personally, I love the "upsell" feature since it easily allows us to leave all the cpanel links/icons in place and then have the customer brought to a sales page where they can order the service they tried to use.
ie: If they sign up for a cheap/starter account that doesn't include mysql databases.. then they still have the link in their cpanel. If they click on it, the rvskin upsell page is displayed and they can quickly see how much it costs, and click "order now" to upgrade.
Just for that feature alone, I recommend rvskin.
It's also nice looking, well organized, and well supported by the developer.
