For any large production Drupal 6 site using mysql, I'm wondering

  • Could it be reasonably possibly to transform to postgresql?
  • Do you know the pros/cons of utilizing postgresql rather than mysql?
  • Does the conversion well worth the effort?
  • What's the simplest method of doing so?

Thanks

I have used it to effectively dump a mysql db to some postgres import file.

http://sqlfairy.sourceforge.net/

Do you know the pros/cons of utilizing postgresql rather than mysql?

The PostgreSQL Optimizer is way better, far better datatype support, faster for anything advanced like triggers/ etc. , really Acidity compliant (nothing like InnoDB the industry fake), triggers on sights, good GIS support, plenty of advanced stuff and much more

May be the conversion well worth the effort?

No, Drupal isn't about advanced SQL and you ought to avoid seeing much improvement switching from MySQL to PostgreSQL, so that as already pointed out you'd lose some compatibility (i.e. everybody uses mysql for drupal pretty much).