Another great article, Paul.
I love reading about your research and experience and thinking about my own research and experience. You are right on in re. to the tags on plants. This also applies to conflicting information on websites and, of course, in catalogs.
Even within the same neighborhood one gardener's experience with a particular plant may vary drastically from another's and micro climates also come into play.
For instance, I have Mexican petunia (tall ruellia http://davesgarden.com/guides/pf/go/38204/#b)
growing up against the south wall of my brick home--the warmest part of my yard. The tag, the research I did, and the owner of a local nursery all said ruellia is not be perennial here. However, in the micro climate in which it is growing it has been very happy (read rampant) for several years.
A friend recently asked for some ruellia to plant out in an open, exposed area unprotected from north wind. I very much doubt that it will survive its first winter, but she wants to try. Since she has sandy soil, and mine is clay, it will be an interesting experiment.