The quality of ATM video is excellent if you have a line of bandwidth 18MB or larger. With less, you might as well use a T1 line. ATM's high speed is great for radiology file transfer or any other image transfer that requires high speed. For telemedicine and most applications, ATM is very nice to have, but not essential. This has to be done by the telecommunications company.
Billing is arbitrary.
There is no way to count gigacell useage. Lack of standards means you need compatible switches at each end, or you are locked into one vendor. Line reliability is not as good as a T1 line. ATM does not error check. Unless you really need the high speed throughput or the highspeed switching, T1 or multiple ISDN lines are still the most reliable, most economical, and most compatible between differnt vendor equipment.