Terry,
I would say its still the major way images are mounted in a pro setting, I have a vac heat press capable of taking a 64" x 44" print and mount larger ones are out there, the mounting tissue is available from a high number of suppliers and places and is made by Hot Press (Drytac), Sealion and quite a few others who I cannot remember off the top of my head, i dare say the ingredients in the adhesive may have changed over time, and there are also more aggressive adhesives for mounting onto a wide range of surfaces. we use the Hot Press adhesives and laminates.
As you say differing temperature adhesive tissue is available, I would warn people to do research before attempting to dry mount as some inks actually change colour when under heat, and some papers will darken when used under heat, for this a cold pressure laminator is best used with pressure sensitive adhesive. On another note we alos use our Hot Press to laminate canvas prints to protect them, very quick easy and non of the mess of varnish or spray fixative.