IPhone 5 Will Have Feature Called Assistant

I was wondering how long it would take for Apple to integrate their Siri acquisition into their products.

Has anybody used the Siri Assistant (I don't have an iOS device) who can give a review of how well it works? The reviews on the app store page don't really give an idea of what it's like.

With built in voice search in WP7 Bing (and I assume Android), is this really something of a differentiator?