Here's an example of qf_form in an app that builds the form on the fly, based on a set of parameters from the product, product variants, and some internal style parameters:
http://birdswelcome.com/configurator?model=abfI really appreciate how qf_* simplifies the coding of the form instead of requiring me to understand the abstractions of ad_form by tweaking a presentation to fit ad_form's limitations or implementation idiosyncrasies. Clearly there's a place for ad_form in general UI consistency, but when an app doesn't fit the ad_form paradigm, it's nice to have the flexible alternative of qf_*.