I've gotta think Apple will open up Siri to app developers sooner than later.
Houndify looks interesting.
The failure rate is high enough that I rarely use the voice feature, despite the fact I have problems with my hands that make typos a constant irritation. I know I am just an anecdote - the strange thing is that my voice and lack of accent should be the easiest thing for Android to navigate.
Maybe try going into Settings > Voice on the Google search app and downloading the voice pack for the version of English you think matches best? That's still pretty weird though.
I think it can augment things well, but not be the prime time star.