I think hydra can totally compete with a mouse, when you use ratcheting, and don't use the freelook mode like in portal where you have a latency in the movements.
Unfortunely the jitter make this mode difficult to use.
I press a buton to control the look, it's also the opposite of the default in the configurator.
On this subject i think maybe there could be a a better solution to ratchet with a pressure sensitive surface that would grab the view when you tend to press the controler more in your hand.
because ratcheting with the thumb makes difficult to use the other buttons.
Also if we have to use our thumb to ratchet, i think there should be a special button with a special shape, a bit bigger than the others. On the wiimote there is a big A button that is in a more obvious location.