ISDN dead?

ISDN dead? If so, then just how do the majority of company switchboards connect to the public phone system?

Yes, we *could* use VOIP and ADSL connections, however these are notoriously unstable, prone to lag and easily interruptable by, say, Patch Tuesday or other times of mass downloads... They also preform VERY badly when sending faxes, establishing remote modem connections and the other wonders of modern business that are still vital.