If you define a data validation proc for your "combo" widget you can then just say "title:combo" in ad_form rather than be forced to remember that it's a select-style widget that is used with "text". I really encourage folks to take this approach when defining new form stuff.
Also it's not that hard to track whether or not you've put out the javascript function and to put it out automatically. This was the approach I took when defining several javascript widgets for Greenpeace.
Then you can use any of the existing form template files ...
