Simon,
The master of the formtemplate is in effect the the .ADP page that holds the formtemplate tag itself, so that page could in turn wrap itself in a master template by putting a <master> tag at the top.
Tom,
if you like the "one page for form presentation/error/submit idea" of the form manager you will LOVE ad_form. It does presentation/error/submit and also edit, all from one tcl/adp pair!
The only package that uses ad_form, to date, that I'm aware of, is the survey package that Dave Bauer recently committed to cvs. That should be a good place to look if you want to see how it works.