Price, peppy engine, driver position and visibility, (for my wife - standard ABS), and a now proven, incredible fuel economy for our worst possible scenario, 2-mile average commute. One suddenly stormy Christmas shopping night with our kids, my son-in-law's full-sized pick-up bed, thought necessary for this excursion, was pushed aside with everything fitting into the easy access xD.
Visibility, handling, simple controls, versatility, economy, safety features, "substantial" feel for such a small car (exterior size). Performance to-date and anticipated reliability, etc.
Fog light option, more standard interior lighting around ignition key, auto-headlights, (a separate brochure/options page from the xB which confused some of above).