The Siri feature on iPhone is simply cool. One of the reasons iPhone remains the go-to-device is because of innovations such as Siri.
Personally, I don't really care to speak to my "personal assistant." Quite frankly, most of the stuff I'd say would be nonsense. Although I guess that one time I needed to "remember" how to tie a bow tie would be important. Of course, then if I was tying a bow tie I'd be insane, have achieved the "upper crust," or become President of the United States, none of which sound all that appealing.
But, if you're dying to be like an "iPhoner," then go ahead an try one of the listed apps.
Spoiler alert: all of the reviews (and I agree) say Vlingo Virtual Assistant rocks.
Vlingo Virtual Assistant