I installed the latest leaked S-Voice and I don't find anything remarkable about it over the standard Google Actions. It does have a more polished user interface, with robotic voice-prompts, and it can be activated from the lock screen (at expense of battery), but it seems to have the same accuracy rate as Google Actions, with a 6-7 more automated tasks pre-established (i.e. like Timer, Record Voice, Social Update, Schedule, etc).
But for the basic stuff like calling and texting contacts, texting, notes, open apps, it's the same. It still doesn't recognize my fiance's name (it's spelled weird) and it's not great at opening apps, both like the standard Google Voice Actions.
So what's all the hoopla about? Is it simply Samsung Marketing trying to promote this as the Siri counterpart?