I've been considering it as a billing solution for my web hosting company. One problem I have with it is that it seems the web server that you have to use to integrate with the filemaker pro database only runs off of windows, kind of contrary to my linux only hosting, no need for a windows server around.

I was wondering who were uses Optigold ISP and what they are doing with it. If you have online access setup for your customers so they can change their billing info, or view invoices, or whatnot.

Any info from people using it would be appreciated.

Thanks

Use ModernBill.

What control panel are you using? If you use cpanel check out WHNBilling.