While Samsung has been a loyal proponent of Android for quite some time, its also spent the past few years cooking up its own open-source mobile operating system called Tizen. After several prototypes and revisions, the company finally saw fit to unveil the Samsung Z — its first ever Tizen smartphone — a couple of days ago. It was easily the star of the show at the Tizen developer conference here in San Francisco, so we were eager to take it for a spin.