Guest WiFi Billing - any experience?

Hi,

Just doing a bit of research and thought I'd see if anyone here has any experience.  I am looking to provide a Guest Wi-Fi service that customers can purchase internet access for a set period of time i.e. 24/48 hours.  I see there are a few companies out there that will provide these services to save me having to setup/manage my own radius servers etc, also they manage all the logging of sessions that is required by law.  Has anyone had any experience with doing this kind of setup, any recommendations or lessons learnt etc.

Cheers
Rob