Yes! Yes! Yes! Packages should be using this and I'd really like to rewrite some that don't to do so in our next release cycle. I've recently fixes some bugs in it (completed the "currency" widget to a "good enough for now" stage, though long-term it needs to integrate with the data in acs-lang; fixed date comparisons etc etc).
In fact I've been thinking a bit about ways to integrate form building with ad_page_contract in order to make form-handling page construction even easier.
