2. (Possibly optional) that the dialog be truly modal - that the
  user not be able to click on other windows while the dialog is
  up. I'm not sure just how important this is, but it seems a common
  programming feature.

I find this to be one of the most annoying features in computers
today.

-- 
Patrick Logan                 mailto:patrickl at gemstone.com
Voice 503-533-3365            Fax   503-629-8556
Gemstone Systems, Inc         http://www.gemstone.com