> even on Android its capabilities are much more limited.
That's not true - in fact, Android has had functionality far beyond Siri's for ages - since FroYo at least if not Eclair or Donut - long before Siri came out. Even Engadget (of all sites!) did a comparison of the two and declared that Android's voice functionality was better.
On top of that, the new (ICS or JB) updates are really fantastic, particularly when you pair them with Google Now.